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Phillips, Molly A. "Snake harassment in the Cape ground squirrel (Xerus inauris): variation in anti-predator behaviours, predator discrimination and venom resistance in a facultative cooperative breeder." Toxicon, 2012. http://hdl.handle.net/1993/9223.
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Predator harassment is an anti-predator behaviour that may increase a harasser’s risk of predation but decrease the potential for predation for other members of a group. The Cape ground squirrel (Xerus inauris) is a facultative cooperative breeder from southern Africa that harasses venomous snakes. The objective of my study was to examine predator harassment to determine: 1) whether predator harassment was part of alloparental care by comparing harassment behaviour among age and sex classes; 2) how individuals adjusted their behaviour against different snake species; 3) whether olfaction was used in discrimination of snakes; and 4) if individuals possessed venom resistance against venomous snakes. I found that females with juvenile offspring harass snakes longer and more intensely than other individuals, suggesting that predator harassment was a maternal behaviour. Squirrels increased harassment, inspection and vigilant behaviours with risk when exposed to both live snakes and snake odours suggesting they can use olfaction to discriminate snake predators. I also found no venom resistance in Cape ground squirrels concluding the cost of envenomation was significant.
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Chabaud, Chloé. "Influence de la balance hydrique sur les interactions trophiques et le risque de prédation chez un mésoprédateur ectotherme terrestre." Electronic Thesis or Diss., La Rochelle, 2023. http://www.theses.fr/2023LAROS009.
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Les changements climatiques actuels impactent les températures environnementales mais également la disponibilité en eau dans les écosystèmes, ce qui peut perturber les interactions trophiques entre proies et prédateurs. Chez les ectothermes terrestres, il existe un conflit physiologique entre la régulation de la température corporelle et de la balance hydrique, mais nous manquons de données pour caractériser les effets des compromis associés sur les interactions biotiques. Cette thèse s’intéresse à cette problématique à travers l’étude écophysiologique et comportementale de traits liés à la thermo-hydrorégulation et aux relations trophiques chez le lézard vivipare (Zootoca vivipara). Ce mésoprédateur généraliste se nourrit d’une grande diversité de proies et est soumis à une forte prédation, notamment par des serpents spécialisés. Les reptiles présentent une grande diversité de traits fonctionnels associés à la thermo-hydrorégulation dont mes travaux caractérisent les déterminants individuels et géographiques chez le lézard vivipare. Ensuite, à l’aide d’approches expérimentales, je montre que la restriction en eau ne peut pas être compensée par l’alimentation chez cette espèce, mais que la nourriture exacerbe les conflits comportementaux entre thermo- et hydrorégulation. Par des observations au laboratoire, j’étudie également les compromis entre hydrorégulation comportementale et évitement des prédateurs. Je démontre que les comportements de détection des prédateurs par la chémoréception augmentent les pertes hydriques et qu’ils sont donc sensibles à la restriction en eau. Ces travaux suggèrent l’existence d’effets des stratégies comportementales de thermo-hydrorégulation sur les relations avec les proies et les prédateursOngoing climate change is affecting environmental temperatures but also water availability in ecosystems, which may disrupt trophic relationships between prey and predators. In terrestrial ectotherms, there is a conflict between the regulation of body temperature and water balance, but we lack data to characterize the effects of the associated trade-offs on biotic interactions. This thesis addresses this issue through the ecophysiological and behavioural study of traits related to thermo-hydroregulation and trophic relationships in the Common lizard (Zootoca vivipara). This generalist mesopredator feeds on a wide variety of prey and is subject to heavy predation, especially by specialized snakes. Reptiles exhibit a large range of functional traits associated with thermo-hydroregulation, and my work characterizes the individual and geographic determinants of these traits in the Common lizard. Then, using experimental approaches, I demonstrate that water restriction cannot be compensated by food intakes in this species, and food actually exacerbates behavioural conflicts between thermo- and hydroregulation. Through laboratory observations, I also investigate the trade-offs between behavioural hydroregulation and predator avoidance. I show that detecting predators via chemoreception increases water loss and this ability is therefore sensitive to water restriction. This work suggests that the behavioural strategies employed by organisms for thermo-hydroregulation can influence the dynamics of predator-prey relationships
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Rhisiart, Alun ap. "Communication and anti-predator behaviour." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333182.
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Jiang, Yiting. "Anti-predator Behavior of Birds and Conservation." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS076/document.
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Prey s'appuie sur les décisions d'évasion lorsqu'il est confronté à des prédateurs pour maximiser les avantages de rester en place tout en réduisant les coûts de la prédation. Ce compromis de l'histoire de vie peut être reflété par la distance d'initiation de vol (FID), la distance à laquelle un individu prend son envol lorsqu'il est approché par un humain. J'ai abordé les facteurs potentiels expliquant la variation FID avec des données d'espèces d'oiseaux en Europe. La variabilité génétique était liée au risque de prédation FID; les espèces d'oiseaux menacées avaient généralement une FID plus longue que les espèces proches non menacées; le caractère distinctif de l'évolution (ED), un indicateur reflétant l'isolement phylogénétique des taxons, était positivement lié à la FID chez les oiseaux d'eau; La FID moyenne de différentes espèces d'oiseaux était positivement corrélée avec les niveaux spécifiques de MDA (malondialdéhyde qui est un indice de stress oxydatif) et UA (acide urique, qui est une mesure de la capacité antioxydante) et FID augmentée avec la taille du troupeau chez les espèces grégaires mais pas chez les espèces non grégaires. Ces résultats peuvent contribuer à la compréhension des causes et des conséquences des différences interspécifiques dans le comportement de fuite des prédateurs contre les prédateurs, et, plus important encore, ils peuvent fournir des moyens de résoudre les problèmes de conservation. Mots-clés : masse corporelle, taille du cerveau, taille effective de la population, modèle linéaire phylogénétique, stress oxydatif, comportement socialPrey rely on escape decisions when confronted with predators to maximize the benefits of staying put while reducing the costs of predation. This life history compromise can be reflected by flight initiation distance (FID), the distance at which an individual takes flight when approached by a human. I addressed potential factors explaining variation FID with data from bird species in Europe. Genetic variability was related to predation risk FID; threatened bird species generally had a longer FID than non-threatened closely related species; evolutionary distinctiveness (ED), an indicator reflecting the phylogenetic isolation of taxa, was positively related to FID in waterbirds; mean FID of different species of birds was positively correlated with species-specific levels of MDA (malondialdehyde which is an index of oxidative stress) and UA (uric acid, which is a metric of antioxidant capacity) and FID increased with flock size in gregarious species but not in non-gregarious species. These findings may contribute to the understanding of the causes and consequences of interspecific differences in anti-predator escape behavior of birds, and, more importantly they may provide means for resolving conservation problems. Key words: body mass, brain size, effective population size, phylogenetic linear model, oxidative stress, social behavior
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Whitwell, Sarah Margaret. "The impact of isolation from mammalian predators on the anti-predator behaviours of the North Island robin (Petroica longipes) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Auckland, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1142.
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Conservation in New Zealand has begun to focus heavily on the restoration of degraded mainland ecosystems and the reintroduction of native species that have become locally extinct. In many cases the individuals that are selected for reintroduction are harvested from ‘mammal-free’ offshore islands. This thesis examines the effects of isolation from mammalian predators on the predator avoidance behaviours and predator recognition abilities of New Zealand birds using the North Island robin as a model. It also investigates whether any effects of isolation from mammalian predators has a lasting impact on mainland populations founded by individuals from offshore islands. Nest site selection behaviours were compared across three populations that are exposed to different suites of predators and have differing translocation histories; Benneydale, Tiritiri Matangi and Wenderholm. Point height intercept and point-centred quarter surveys were used to compare habitat availability between the sites and to compare nest sites with the available habitat. Eight nest characteristic variables were also compared across the three sites using a principle component analysis. Benneydale nests were located higher in the trees and were more concealed than nests at the other two sites. Nests on Tiritiri Matangi were supported by large numbers of thin branches and were located toward the periphery of the nest tree. Unfortunately these differences are very difficult to interpret due to a high degree of variation in the habitat types present at the three sites. The anti-predator behaviours initiated in response to a model stoat, model morepork and control were used to test the ability of nesting robins to recognise the threat that each of these treatments might pose to nest success. Behavioural variables were compared between Benneydale, Tiritiri Matangi and Wenderholm using a response intensity scoring system and a principle component analysis. The results indicated that isolation from mammalian predators on Tiritiri Matangi has suppressed the ability of robins on the island to recognise the predatory threat posed by a stoat. They also suggest that the intense mammal control carried out at Wenderholm may have inhibited the ability of local robins to produce strong anti-predator responses when faced with a stoat.
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Carlson, Nora. "Anti-predator behaviour in UK tit species : information encoding, predator recognition, and individual variation." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/11366.
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To combat the ever-present threat of predation many species produce anti-predator vocalizations and behaviours (mobbing) designed to drive predators away. These vocalizations can encode a predator's threat level, and many species within a community will eavesdrop on this information. To determine how prey species produce, use, and respond to anti-predator information and how individual, social, and phylogenetic factors of different species may influence this behaviour, I conducted a series of robotic-predator presentation and anti-predator vocalization playback experiments in the wild and lab. I predicted that UK Paridae would encode information the same as previously studied species. I found that UK Paridae encode predator information in different ways, and that neither phylogeny nor ecology explained the patterns of similarity in how different species encode predator threat in their calls. Flock structure appeared to affect how species encoded predator threat and while multiple species may be sources of information for familiar flock mates, only blue and great tits met the criteria to be community informants. As blue and great tits need prior experience to recognize novel predators and juvenile great tits avoid novel predators only after seeing adults mob them, tits may use mobbing calls to learn about novel predators. While they responded to mobbing calls, juvenile blue and great tits did not engage in mobbing behaviour although they appear capable of doing so. Furthermore, while individuals varied in their responses to aerial alarm calls this variation was not explained by either their proximity to the call nor their personality. In this close examination of how anti-predator vocalizations are produced and used by UK Paridae, I found variation in these signals. This challenges previous assumptions about how Paridae encode information, raising questions as to the sources of this variation.
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Schel, Anne Marijke. "Anti-predator behaviour of Guereza colobus monkeys (Colobus guerez) /." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/832.
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Black-and-white colobus monkeys are renowned for their impressive vocal behaviour, but up to date there have been only very few systematic efforts to study this. These monkeys are able to produce loud and low-pitched roars that transmit over long distances, which has lead to the assumption that these calls function in inter-group spacing and male-male competition. The fact that the monkeys sometimes produce the same calls to predators as well, has not received much attention so far. This thesis presents a detailed description of the form and function of the anti-predator behaviour of one species of black-and-white colobus monkeys, the Guereza (Colobus guereza), with a specific focus on their alarm calling behaviour. A second aim was to determine the effects of predator experience on their anti-predator behaviour, with a specific focus on call comprehension and production. Data were collected from two populations of Guereza monkeys in the Budongo Forest Reserve, Uganda, that differ in predation pressures experienced by their main predators: leopards, eagles and chimpanzees. Results showed that Guerezas use a basic form of zoo-syntax in order to compose predator-specific call sequences that vary in the number of roaring phrases and snorts. These sequences are meaningful to recipients, at least at the level of the predator class, but there were also indications for additional levels of encoded information: Guerezas appear to have evolved a second system, based on acoustic variants of individual phrases, which allows them to narrow down the information content of call sequences, generating the potential to communicate highly specific information by using a mix of syntactic and semantic cues. The monkeys’ vocal behaviour was influenced by predator experience, but not strongly so. Monkeys without prior experience with leopards lacked some of the behavioural nuances seen in leopard-experienced monkeys, but they nevertheless responded appropriately to visual and acoustic leopard models, suggesting they had retained the basic capacities to recognise this predator type as relevant and dangerous. Results are discussed in light of the comparative approach to the study of human language evolution. Although human language is unique in a number of ways, for example through its use of complex syntax and intentional semantics, some animal communication systems have revealed similar features, and Guerezas, the first member of the colobine family to be studied in this respect, are no exception. The Guerezas’ alarm calling behaviour is complex and flexible, and these monkeys have provided another piece of empirical evidence that is directly relevant for the comparative approach to human language evolution.
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Dalesman, Sarah Joanne. "Anti-predator behaviour in the freshwater gastropod Lymnaea stagnalis." Thesis, University of Plymouth, 2007. http://hdl.handle.net/10026.1/2707.
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The freshwater gastropod Lymnaea stagnalis was used as a model organism to investigate the mechanisms employed by prey species to fine-tune anti-predator behaviour to match their environment. Lymnaea stagnalis was found to exhibit both genetic adaptation of innate responses and also induced responses to predator cues. Snails were also capable of responding to predation cues via associative learning dependent on recent experience. Constitutive responses were found to differ between populations depending on the predator regime that the population experienced in the wild. Artificial selection produced in only two generations a difference in the magnitude of response between high and low response selected lines equal to those seen between field populations in two generations. At the same time these selected lines maintained phenotypic plasticity and responded to exposure to predator cues during development. This developmental plasticity led to an increased response to predation cues in the low selected line equivilent to that in the high response selection line; a lack of induced change in behaviour in the high response selection line suggested a physiological limitation on the maximum anti-predator response. The response in the low selection lines indicates that plasticity in anti-predator behaviour could allow individuals with low innate responses to compensate with high levels of induced response. Finally, L. stagnalis was able to utilise alarm cues from prey guild members (i.e. other freshwater gastropods) to assess predation risk, a response that was dependent on the phylogenetic relationship between L. stagnalis and the species producing the alarm cue. However, this response was dependent on whether the species was found sympatrically ( cohabiting the same water body) with L. stagnalis. Together, the rapid microevolution of constitutive responses in L. stagnalis, its ability to show induced responses and associative learning indicates that this species may be able to respond rapidly to a novel predation environment, and therefore allow colonistion of new habitats or identification of novel predators.
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Dowell, Simon Derek. "The ontogeny of anti-predator behaviour in game bird chicks." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257814.
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Ca¨sar, Cristiane. "Anti-predator behaviour of black-fronted titi monkeys (Callicebus nigrifrons)." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/2575.
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Titi monkeys have long been known for their complex vocal behaviour with numerous high- and low-pitched calls, which can be uttered singly or combined in more complex structures. However, up to date very little is known concerning the function, meaning and context-specific use of these vocal utterances, and virtually nothing is known about their vocalisations in the predation context. This thesis presents a detailed description of the form and function of the anti-predator behaviour of one species of titi monkeys, the black-fronted titi monkey (Callicebus nigrifrons), with a specific focus on their alarm call behaviour. A second aim was to determine the exact mechanisms of alarm calling behaviour, with an emphasis on production and comprehension. Data were collected from several habituated groups in the Caraça Reserve, Minas Gerais, Brazil. Results showed that, when detecting predator species, C nigrifrons produce sequences that initially contain two types of brief, high-pitched calls with distinct frequency contours. Further evidence suggested that some of these sequences are meaningful to conspecific receivers, by indicating the general predator class and location of threat. There were also indications that, within the terrestrial threats, additional information may be encoded by acoustic and compositional differences. Analyses of call order and number of calls per sequence suggested that callers may be able to convey information on both predator type and location. The black-fronted titi monkeys’ vocal system thus provides a further example of zoo-syntax, in which acoustically fixed units of a vocal repertoire are combined into higher order sequences that are meaningful to recipients. According to current definitions, this type of calling behaviour qualifies as functionally referential, by indicating general predator class, terrestrial predator type and location. As such, this is the first empirical demonstration of a sequence-based alarm call system that conveys information on both predator category and location.
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Westrip, James Robert Samuel. "Organisation & development of anti-predator behaviour in a cooperative breeder." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25389.
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In order to reduce their predation risk, species have evolved a range of anti-predator behaviours. One co-ordinated anti-predator behaviour present in some group-living species is sentinel behaviour. In this behaviour individuals take up an elevated position and scan for threats, providing an alarm when one is spotted. However, this behaviour can lead to social conflict. Sentinel behaviour is a public good, i.e. the benefits are felt by all group members, but the costs only accrue to the actor. Thus it may be open to free loading, requiring individuals to monitor collaborators to prevent cheats. Additionally, individuals may vary in their alarm call reliability, which may select individuals to alter their behaviour based on caller ID. Monitoring others requires individuals to be closely associated, yet individuals may be spread out. For instance, foraging groups may be some distance from their nest, yet nestlings are particularly vulnerable. Adults should reduce their number of nest visits if a threat is nearby, so individuals returning from the nest may be selected to communicate about any perceived threats. Additionally, when perceiving threats, species need not use only conspecific information, because heterospecifics can also provide relevant information. In this thesis, I test these ideas in the Southern Pied Babbler (Turdoides bicolor), and I show that a) pied babblers monitor the quantity and quality of group-mates’ anti-predator behaviour; b) babblers accompany naïve sentinels and I investigate whether this may be related to anti-predator teaching; c) babblers do not appear to actively communicate about perceived nest threats because they do not alter their provisioning rate based on heterospecific derived anti-predator information; while d) avian heterospecifics are more prevalent in the presence of pied babblers, and can be attracted to areas by playback of pied babbler calls. These results show that species monitor both conspecifics and heterospecifics, and alter their behaviour based on the information they collect.
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Kotschwar, Mary Wynne. "Variation in predator communities and anti-predator behaviors of Milne-Edwards' sifakas (Propithecus edwardsi) in southeastern Madagascar." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/34266.
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To advance conservation in the increasingly fragmented landscape of Madagascar, we must examine the persistence and interactions of species in human-disturbed habitats. I investigated lemur-predator interactions in southeastern Madagascar through a comparison of predator communities and anti-predator behaviors of Milne-Edwards' sifakas (Propithecus edwardsi) in the continuous rainforest of Ranomafana National Park, and the forest fragments of Ialatsara Forest Station. I confirmed the presence of potential aerial predators at each site, but the sifakas' confirmed native mammalian predator, fossa (Cryptoprocta ferox), was absent from the fragmented site. Playbacks of predator vocalizations did not suggest that fragment-living sifakas have weakened anti-predator responses, but that their responses may be less specific than those of conspecifics in the continuous forest. I found that fragment-living sifakas displayed less downward vigilance and more frequently used low canopy heights; these behaviors may increase their vulnerability to recolonizing ground predators. I investigated local ecological knowledge (LEK) of carnivore ecology in communities 0–20 km from continuous forest to explore the potential for such recolonization. My findings from 182 interviews in 17 communities suggest that the fossa is especially sensitive to anthropogenic disturbance; it was only observed in communities ≤ 2.5 km from the continuous forest within the last five years. In contrast, the introduced small Indian civet (Viverricula indica) and wild cat (Felis silvestris) were distributed ubiquitously and displayed an affinity to human-dominated habitats. LEK surveys can provide information on the poorly understood responses of the Malagasy carnivores to the threats they face in a changing landscape.Master of Science
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Hofling, Annika. "Do enclosure characteristics affect anti-predator behaviour in the European bison (Bison bonasus)?" Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19942.
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Animals raised in captivity often fail to express appropriate anti-predator behaviour when reintroduced into the wild. The European bison (Bison bonasus) is a species that was close to extinction in the early 20th century but was saved in the last moment by intense captive breeding and subsequent reintroduction into the wild. In this study, seven groups of European bison living in different locations in Sweden were studied to investigate whether there was any difference in the anti-predator behaviour depending on the type of enclosure they were kept in. Olfactory and auditory stimuli from moose, as a control, and from two predators, wolf and bear, and visual stimulus (silhouette of a wolf) were presented to the animals and their response to them and behaviour following presentation were analysed. The results showed that European bison kept in barren enclosures responded stronger to auditory stimuli than those that were kept in naturalistic enclosures. The results further showed that the animals had a stronger response to the visual stimulus than to the auditory stimuli. The animals changed their behaviour after stimuli presentations compared to a pre-test baseline. They moved, stood still and ate for a significantly longer period of time and they rested for a shorter period of time after being presented olfactory, auditory and visual stimuli than during pre-test baseline.
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MELOTTO, ANDREA. "ANTI-PREDATOR RESPONSES TOWARDS AN INVASIVE CRAYFISH IN AMPHIBIAN LARVAE." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/714592.
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Invasive species pose a severe threat to native ecosystems and represent the second cause of biodiversity loss on global scale after habitat destruction.
In particular, invasive predators are major drivers of rapid population declines and local extinctions in native prey. During biotic invasions, native prey become abruptly exposed to novel predators with which they share no history of coevolution. Thus, the lack of common evolutionary history often hampers prey effective response to the novel predation pressures; native prey can both fail to recognise predators as a threat and exhibit anti-predator strategies that are inadequate. Nonetheless, mechanisms such as rapid adaptation and phenotypic plasticity can allow prey to cope with new selective pressures and drive evolutionary changes that can help native species withstanding invasive ones.
Due to their relative ecological isolation, freshwater ecosystems are particularly sensitive to invasive species impacts and likewise are most of the organisms exploiting them like amphibians; aquatic and semi-aquatic amphibians are effective indicators of freshwater habitats conservation with an excellent potential for studying the responses towards invasive species. Indeed, generally, amphibians show high level of developmental and behavioural plasticity and have relatively short life cycles, which could allow the detection of important adaptive patterns even few years after the spreading of invasive organisms.
This thesis investigated how amphibians can respond to a novel predation pressure, by assessing their modulation of anti-predator responses on multiple traits (i.e. behavioural morphological, life-history). In particular, I aimed to shed light on (i) the role of phenotypic plasticity in mediating the expression of anti-predator responses towards invasive predators; (ii) how novel predation pressures can interact with extant selective forces and foster rapid adaptation in native prey; and (iii) which evolutionary mechanisms are involved in allowing predator recognition by naïve prey.
To this extent, I evaluated the expression of anti-predator responses in amphibian larvae towards the American red swamp crayfish (Procambarus clarkii). This widespread crayfish is listed among the 100 worst invasive alien species, and is a voracious predator of amphibian eggs and larvae, often associated to strong declines of amphibian populations outside its native range.
In brief, the research consisted in two main experimental studies, the first of which focused on developmental shifts of a single anuran species, while the second one assessed behavioural responses to the invasive crayfish across the amphibian community of Northern Italy.
In the first study, I exposed tadpoles of an endemic frog (Rana latastei) from recently invaded (10- 15 years) and uninvaded populations to the non-lethal presence of the invasive crayfish during their ontogenesis. Tadpoles from invaded populations showed rapid adaptation in life-history traits (reduced development time), and this caused the disappearance of pre-existing adaptive divergence between R. latastei populations exploiting environments with different climatic regimes. However, even if early metamorphosis in invaded populations probably has great advantages as it reduces exposure to crayfish predation, this shift can produce potential carry-over effects on post-metamorphic traits. Indeed, the observed development acceleration was not without a cost, as faster-developing froglets were smaller and displayed poorer jumping performances.
Besides, experimental exposure to the invasive crayfish revealed tadpoles were also able to modulate both their development time and morphological traits through phenotypic plasticity. An acceleration in development time was observed even in exposed tadpoles. Moreover, tadpoles reared in presence of P. clarkii showed shift in body shape together with an increase in tail muscle size, which is a trait associated to faster swim and can increase escape from predators. By contrast, tadpole behaviour was not influenced nor by origin (invaded or not invaded populations) neither by crayfish exposure.
The second study was performed on several species composing Northern Italy amphibian community (five urodele and eight anuran species); for each species I assessed how different stimuli mediated novel predator recognition and elicited the expression of anti-predator responses in naïve species. To this extent, I evaluated multiple larval behavioural traits after brief non-lethal exposure to crayfish-released cues (four treatments: visual cues, chemical cues, contemporary exposure to both cues and control). Moreover, I tested if these responses were influenced by the coevolutionary history some of these species shared with a similar native predator, the European crayfish (Austropotamobius italicus). I showed that all species altered their behaviour when exposed to the invasive crayfish while the modality and intensity of response was highly heterogeneous. However, almost all behavioural responses were driven by visual cues, while chemical cues elicited feeble and contrasting outcomes. Finally, I found no support for a coevolutionary history hypothesis between native amphibians and native crayfish, as responses to the invasive predator were not affected by species coexistence with native crayfish. Instead, behavioural responses observed in naïve species was likely elicited by recognition of general predator traits (e.g. an approaching large shape).
The broad implication of my thesis is that amphibian facing invasive predators can both exhibit rapid adaptation to the novel selective pressures and modulate their developmental traits through phenotypic plasticity. Moreover, the expression of these responses is context-dependent and can highly vary in relation to the experienced conditions and across species. For instance, varying typology of risk exposure can produce marked difference in anti-predator response (e.g. activation of short-term behavioural response vs long-term morphological responses). Future studies assessing responses to invasive predators should evaluate multiple traits and carefully consider risk exposure conditions when planning experiments. Finally, the expression of anti-predatory responses of native amphibians, and particularly their effectiveness towards invasive predators, need further extensive investigation, and future conservation plans should take into account both species trends and their responsiveness to global change stressors.
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Okamoto, Kohei. "Behavioral study of expression of body patterns for avoiding predation in the pharaoh cuttlefish Sepia pharaonis." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202665.
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Lohrey, Anne K. "The Impact of Avian Predation on the Brush-Legged Wolf Spider, Schizocosa Ocreata (Hentz), and Anti-Predator Responses to Avian Cues." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195846324.
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Bryer, Pamela J. "The Embryonic World of Wood Frogs, Rana Sylvatica: Natal Pond Learning and Anti-Predator Behaviors." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/BryerPJ2002.pdf.
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Johansson, Martin. "Effects of an anti-anxiety drug on predator-induced behavior in a boreal frog species." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-178792.
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Pharmaceuticals polluting natural environments pose a greater and greater threat in today’s society. Benzodiazepines, the most common form of anxiolytic drug, can commonly be found in nature as a result of the release of human wastewater containing the drug, and have been shown to affect both fish and frog species in several different ways related to predator evasion. This study aims to determine whether a common benzodiazepine, oxazepam, has any inhibitory effect on induced behavioral defenses in the boreal frog species Rana temporaria. Larvae of R. temporaria were exposed to an oxazepam gradient, paired with three different predator regimes consisting of a control, an ambush-predator setting, and a pursuing-predator setting. The larvae were then filmed at three different Gosner stages during simulated predator encounters, while measuring maximum velocity and acceleration, as well as activity- and exploration level, and the duration of avoidance following each encounter. Tail related morphological traits were also measured in order to correlate velocity and acceleration with trait properties. Avoidance duration was found to decrease when exposed to ambush predators, regardless of oxazepam concentration. No other effect of predators could be found during this study, and no significant correlations between tail properties and velocity or acceleration were seen. Oxazepam was not found to inhibit any induced behavioral defenses, nor did it alter any of the examined behavioral traits.
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Connolly, Lauren E. "Effect of predator diet on foraging behavior of panopeus herbstII in response to predator urine cues." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/53392.
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The ability of prey to detect and respond appropriately to predator risk is important to overall prey fitness. Many aquatic organisms assess risk through the use of chemical cues that can change with predator diet. Two variable characteristics of diet are: 1. prey type and 2. prey mass. To assess the effect of these two characteristics on the assessment of risk by the mud crab Panopeus herbstii, I exposed mud crabs to the urine of the blue crab Callinectes sapidus fed one of 5 diet treatments: 10g of oyster shell free wet mass, 5g of oyster shell free wet mass, 10g crushed mud crabs, 5g crushed mud crabs, and a mix of 5g of oyster shell free wet mass and 5g crushed mud crab. Effects on P. herbstii foraging were tested in a previously developed bioassay by measuring shrimp consumption over a 4 hour period. I hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a diet of crushed mud crabs than to urine from C. sapidus fed a diet of oysters. I further hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a high mass diet relative to a lower mass diet. Contrary to expectations there was no observed effect of urine on P. herbstii foraging in any of the treatments. Results suggest that bioassay protocol may be unreliable suggesting further replication to determine the difference between this study and previous results. Future studies examining how P. herbstii varies with urine concentration will aid in understanding the ecological scale of this predator cue system. Determining the role of other potential cue sources will improve the predictive abilities of these studies.
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Vitale, Augusto F. "Development of dispersionary and anti-predator behaviour in young wild rabbits (Oryctolagus cuniculus (L.)) in sand dunes." Thesis, University of Aberdeen, 1988. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU010242.
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Patterns of dispersion of young wild rabbits, in relation to conspecifics and burrows, were studied in a wild population of young rabbits in a sand dune habitat. In general, no significant age-related changes in mean nearest-neighbour distances were observed. Although littermates were closer than expected by chance, young rabbits spent more time on the surface with non-related young than with a mixture of littermates and non-littermates. Nearest-adult distances were very close to those expected by chance. Unrelated young tended to diverge from each other when closer than 1m, but this effect was not observed at greater nearest-young distances. More divergent movements than convergent ones were also observed in the case of different nearest-adult distances. It is suggested that for young rabbits in a sand dune population kin-group cohesion is not an important characteristic of the social system. Young rabbits did not show a close association with their original burrow; from the first week of life on the surface, they used different burrows. No significant age-related changes in the mean distance from different kinds of burrows were observed. The mean distance from the nearest burrow remained always under 3m, but this may have been due largely to the high density of burrows. The apparent freedom of movements of young rabbits between different burrows may be related to the social system of the adults. The frequency of sitting alert increased with age in 1984, but it decreased the following year and predictions about the relationship between vigilance and social behaviour were not confirmed. On the other hand, lying and feeding remained nearly constant with age, but the frequency of lying was higher at less than 1m from the burrow than at greater distances. Both maturation/learning processes and external factors appeared to influence the development of behaviour of young rabbits. The effects of age and experience on anti-predator responses were followed using different models of predators. Baby rabbits showed greater alertness than older individuals. Experienced rabbits, more than inexperienced ones, showed different responses to different stimuli. It is suggested that some form of learning improves the quality of anti-predator responses.
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Adams, Dara B. "Risk Perception, Alarm Call Usage, and Anti-predator Strategies in an Amazonian Primate, Pithecia rylandsi." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1593533930462016.
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Heckmann, Jonathan Gardner. "Effects of atrazine, chlorpyrifos, and their interactions on anti-predator behavior and activity in African clawed frogs, Xenopus laevis." Thesis, Wichita State University, 2009. http://hdl.handle.net/10057/2428.
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Two separate experiments were conducted to examine potential mixture effects of chronic, sub-lethal concentrations of atrazine and chlorpyrifos on the alarm response and activity of larva of the African clawed frog, Xenopus Laevis. Larvae were exposed to three concentrations of atrazine, (0, 20, and 200 μg/L), three concentrations of chlorpyrifos (0, 1, and 10 μg/L), and all possible combinations of those doses for a period of two weeks prior to behavioral testing.
Activity of larvae was evaluated by measuring both how many seconds the larvae spent active in any way and also by measuring the number of times the larvae crossed the center line of their experimental container. Alarm responses were provoked by introduction of an “alarm substance,” to which larvae reacted by exhibiting anti-predator behavior. This alarm response was evaluated by measuring the amount of time spent active before and after alarm substance introduction (depressed activity is the typical alarm response), as well as the amount of time spent opposite the end of the experimental container where the alarm substance was introduced. Behavioral trials were videotaped for purposes of data collection.Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Biological Sciences
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Otsuki, Hatsune. "Interactions between Spider Mites and Predators in Systems with Dispersal Opportunities." Kyoto University, 2020. http://hdl.handle.net/2433/253311.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第22475号
農博第2379号
新制||農||1074(附属図書館)
学位論文||R2||N5255(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 日本 典秀, 教授 田中 千尋, 准教授 刑部 正博
学位規則第4条第1項該当
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Wilson, Rebecca. "Investigating the Interaction of Monoamines and Diel Rhythmicity on Anti-Predator Behavior in an Orb-Weaving Spider, Larinioides cornutus (Araneae: Araneae)." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etd/3441.
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Circadian rhythms are ubiquitous among organisms, influencing a wide array of physiological processes and behaviors including aggression. While many neurophysiological mechanisms are involved in the regulation of aggressive behaviors, relatively few studies have investigated the underlying components involved in the interplay between circadian rhythms and aggression. Spiders are an ideal model system for studying circadian regulation of aggression as they are ecologically both predators and prey. Recent studies have revealed a nocturnal orb- weaving spider Larinioides cornutus exhibits a diel and circadian rhythm in anti-predator behavior (i.e. boldness) that can be manipulated by administration of octopamine (OA) and serotonin (5- HT). Dosing of OA increases boldness of an individual while 5-HT decreases boldness levels. Thus, it appears the serotonergic and octopaminergic system are playing a key role in the daily fluctuations of boldness. This study took a holistic approach to investigate OA and 5-HT levels of head tissue and hemolymph (i.e. blood) as well as the genes involved in synthesis, signaling, and degradation of these monoamines throughout the day (0100, 0700, 1300, and 1900 hours) using HPLC-ED and RNA-sequencing. Although endogenous and circulating levels of OA did not significantly fluctuate, putative transcripts involved in synthesis and signaling did increase in relative expression levels at dusk when L. cornutus begins to actively forage for prey. Endogenous and circulating levels of 5-HT also did not significantly change at the four different time points, but clear patterns of upregulation of 5-HT synthesis enzymes as well as some receptor transcripts were upregulated during the day when L. cornutus would be mostly inactive in its retreat. Lastly, monoamine oxidase, a major catabolic enzyme of monoamines in vertebrates and some invertebrates, was identified in L. cornutus and exhibited substrate specificity for OA compared to 5-HT. Together with the higher enzymatic activity at mid-day compared to dusk, MAO appears to be playing a significant role in regulating the OA and 5-HT signaling in L. cornutus. In conclusion, these results allow a unique preliminary perspective on how OA and 5-HT are influencing the diel shifts in aggression-related behaviors in an ecologically dynamic arthropod.
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Patin, Rémi. "Jeu spatial et interactions comportementales dans la relation prédateur-proie." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG035/document.
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Prédateurs et proies sont entraînés dans une course spatiale où les prédateurs cherchent à sélectionner les zones du paysage avec une forte disponibilité en proies alors que les proies tentent d’éviter les zones du paysage avec une forte probabilité de rencontrer un prédateur. Ils procèdent incessamment à de nombreux choix susceptibles de modifier l’issue de cette course. Ainsi, en sélectionnant des endroits différents, ils peuvent tenter d'altérer les probabilités de détection, de rencontre ou encore la probabilité de réussite d’une attaque. De nombreuses études empiriques montrent l’importance de l’habitat dans ces choix. On connaît par contre peu les mécanismes de recherche (par les prédateurs) ou d’évitement (par les proies) qui ne seraient pas relatifs à l’habitat. La course spatiale ne résume cependant pas entièrement l’interaction entre prédateurs et proies, laquelle dépend de nombreux comportements non-spatiaux. La vigilance et la socialité des proies constituent des défenses relativement répandues. On a aussi fréquemment observé de nombreux exemples où les proies deviennent actives à un autre moment de la journée pour échapper à leur prédateur. Cependant, on connaît relativement peu les interactions de ces comportements avec la dimension spatiale du jeu proie-prédateur. Dans cette thèse, j'ai pour objectif de combler ces différents manques. Dans le premier chapitre, je propose un modèle théorique montrant l’importance de la prise en compte des comportements spatiaux dans l’interaction classique entre vigilance et taille de groupe chez les proies. Dans le second chapitre, je présente un mécanisme d’évitement des prédateurs par les proies, s'appuyant sur les ancres spatiales et temporelles des prédateurs et ne dépendant pas de l’habitat. Enfin, dans le dernier chapitre, je développe un modèle de choix de parcelles permettant de prévoir comment les connaissances passées sont susceptibles d'être utilisées pour orienter les déplacements. Ce modèle rappelle notamment l’importance de l’imprévisibilité du déplacement dans le jeu prédateur-proie. Ces différents travaux se placent dans le cadre d’une écologie comportementale du paysage et visent à intégrer des mécanismes comportementaux dans l’étude des dynamiques écologiques à l’échelle du paysagePredators and prey engage into a space race where predators seek to select areas with high prey availability while prey try to avoid areas with a high probability of encountering a predator. Predators and prey continuously make choices that can alter the outcome of this space race. For example, by using different locations in the landscape, they can alter the probability of an encounter, the probabilities of detection or the probability of success of an attack. Many empirical studies show the importance of habitat in these choices. On the other hand, little is known about avoidance by prey or predator search strategies that would be unrelated to habitat. The space race, however, does not fully summarize the interaction between predators and prey, which also depends on many non-spatial behaviors. The vigilance and grouping behaviour of prey are relatively common defenses, and there are many examples where prey become active at another time of day to escape their predator. However, it is still unclear how those behaviors interact with the spatial dimension of the prey-predator game. In this thesis, I will try to fill these gaps. In the first chapter, I propose a theoretical model showing the importance of accounting for spatial behaviors when studying the classical interaction between vigilance and group size in prey. In the second chapter, I present a mechanism of predator avoidance by prey, relying on the spatial and temporal anchors of predators and independent on the habitat. Finally, in the last chapter, I develop a patch selection model to predict how past information should be used to determine movement. This model emphasize the importance of movement unpredictability in the predator-prey game. These different works are part of a behavioral ecology of the landscape and aim to integrate behavioral mechanisms in the study of ecological dynamics at the landscape scale
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De, Vos Alta. "Anti-predator behaviour of Cape fur seals Arctocephalus pusillus pusillus in relation to predation by white sharks Carcharodon carcharias around Seal Island, False Bay, South Africa." Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/10423.
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Includes bibliographical references (leaves 161-202).How predators affect the behaviour of their prey is one of the most studied subjects in behavioural ecology, with many hypothesis and models explaining how animals should behave and even more descriptive studies detailing how they do. The unification of the empirical with the theoretical, however, remains limited. The overall aim of my thesis was to address this paucity at Seal Island, South Africa, where recently quantified patterns of predation pressure by white sharks Carcharodon carcharias on Cape fur seals Arctocephalus pusillus pusillus suggested a landscape of fear particularly apposite to this.
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Van, Der Meer Ester. "Is the grass greener on the other side? : testing the ecological trap hypothesis for African wild dogs (Lycaon pictus) in and around Hwange National Park." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10095/document.
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Lorsque des animaux montrent un choix préférentiel pour un habitat à effet puits, on dit alors qu’ils sont capturés par un piège écologique. La sélection de l’habitat est bénéfique dans les systèmes classiques de type source-puits, puisque les animaux vivant dans des habitats de haute qualité (natalité>mortalité), choisissent de migrer vers des habitats de faible qualité (natalitéWhen animals show a preferential choice for sink habitat they are said to have been caught in an ecological trap. Habitat choice behaviour is beneficial in classic source-sink systems, as animals living in high quality habitat (natality>mortality) only choose to migrate into low quality habitat (natality
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Cannas, Marcella. "Effets des polychlorobiphényles et de l’hypoxie sur l’énergétique, les performances cardiaques et le comportement anti-prédateur chez les juvéniles de sole commune (Solea solea)." Thesis, La Rochelle, 2011. http://www.theses.fr/2011LAROS331/document.
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La zone côtière Atlantique constitue une importante nourricerie pour les juvéniles de sole commune (Solea solea, Linnaeus 1758). Pour évaluer les conséquences sur la biologie des juvéniles de cette espèce exploitant un milieu côtier de plus en plus anthropisé, les effets de l’hypoxie et/ou des Polychlorobiphényles (PCBs) ont été évalués sur leurs performances physiologiques (métabolisme aérobie et performances cardiaques) ainsi que sur leur comportement vis-à-vis des prédateurs. Pour cela, une étude a été réalisée à deux échelles d’organisation biologique, l’organe et l’individu. Des contaminations aux PCBs (670 ng and 2239 ng PCB g-1 de nourriture ont été effectuées expérimentalement par voie trophique pendant 30 et 60 jours. De telles expositions ont engendré des effets peu marqués sur le métabolisme aérobie, se traduisant par une faible augmentation du métabolisme de maintenance associé à une augmentation de la concentration critique en oxygène (O2crit) chez les soles exposées sur le long terme à la plus haute concentration de PCB. De la même façon, la performance cardiaque n’est apparue que très peu affectée par la contamination aux PCBs. Nous avons tout de même noté une diminution de la force de contraction du cœur des soles contaminées lorsqu’il est fortement sollicité comme c’est le cas au cours d’une activité physique soutenue. Par ailleurs, le mécanisme de contraction du cœur se trouve modifié chez les soles contaminées avec une participation plus importante du calcium issu du réticulum sarcoplasmique que chez les soles témoins. Les résultats concernant le comportement anti-prédateur ont montré que l’hypoxie engendrait une réduction du taux de réponse de fuite de la sole, ainsi qu’une limitation de leur capacité cryptique via une augmentation oxy-dépendent de la fréquence de ventilation. D’une façon générale, même si les PCBs semblent avoir peu d’effets sur les performances physiologiques testées, il ne peut être exclu qu’ils puissent compromettre à plus long terme le développement et la survie des juvéniles de soles, qu’ils soient associés ou non à des conditions environnementales limitantes comme l’hypoxieThe Atlantic coastal zone constitutes an important nursery for the juveniles of the common sole (Solea solea, Linnaeus on 1758). To assess the effect of anthropisation on the survival of the juveniles of common sole, the effects of the hypoxia and\or Polychlorinated Biphenyles (PCBs) on their physiological performances (aerobic metabolism and cardiac performances) were assessed as well as their antipredator behaviour. For that purpose, the study was carried out at two levels of biological organization, the organ and the individual. Sole contamination with PCB (670 ng and 2239 ng PCB g-1 of food), was made experimentally via the trophic pathway, during 30 and 60 days. Our results suggest that PCBs slightly affected the aerobic metabolism. An increase of the standard metabolic rate participate to raise the level of critical oxygen concentration (CritO2) in soles exposed to long term to the highest concentration of PCB was noted. In the same way, the cardiac performances seem to be slightly affected by PCB-contamination. A decrease in the peak tension was noted in PCB-contaminated soles forced to an intense activity. In addition it was noted an increase in the participation of the sarcoplasmic reticulum to the force of contraction in the hearts of soles contaminated compared with hearts of control soles. The results obtained with regard to the simulation of the attack of a predator showed that responsiveness was lower in hypoxia compared with normoxia associated with a decrease of their cryptic capacity. In general, even if the PCB seems to have slight effects on the tested physiological performances, it cannot be excluded that long term exposure to PCBs can compromise the development and the survival of the juveniles of common sole, independently of their association with limiting environmental conditions such as hypoxia
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Hietanen, Kai-Henrik. "Akuta och kroniska effekter av fluoxetin på antipredatorbeteende hos Asellus aquaticus." Thesis, Linköpings universitet, Biologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-138585.
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Fluoxetin är den aktiva substansen i många serotoninreglerande läkemedel som förs in i vattendrag. Substansen har visats påverka beteende av vattenlevande organismer som fiskar, mollusker och kräftdjur genom att öka deras djärvhet. I denna studie undersöktes fluoxetins akuta (på vildfångade individer) och kroniska (på labbuppfödda individer) effekter av koncentrationerna 0, 3 och 30 ng L-1 på Asellus aquaticus (sötvattengråsugga) antipredatorbeteende. Detta gjordes genom tre beteendetest: (1) tid att lämna refug, (2) spontan aktivitet samt (3) flyktbeteende under predationsrisk. Överlag hittades få eller inga effekter på A. aquaticus från fluoxetin. De effekter som dock påverkade individer signifikant visade att exponerade individer flydde en signifikant kortare (30 %) tidsperiod från en simulerad predatorattack. Utöver denna huvudeffekt av fluoxetin hittades även signifikanta skillnader i fluoxetins påverkan på de två grupperna, när individer blev utsatta för den högsta koncentrationen ökade vildfångade individer sin aktivitet (38 % fler stopp och 49 % mer rörelse) medan labbuppfödda individer sänkte sin aktivitet (43 % färre stopp och 37 % mindre rörelse). Individer som inte var exponerade visade signifikanta skillnader i alla beteendetest för de två grupperna. Det är troligt att beteendeskillnader är en följd av olika uppfödningsmiljöer, dock går det inte att utesluta att ändrade genfrekvenser uppkommit. Studien lyser sken på behovet av fler studier av långtidsexponering av läkemedelsrester, de är sällan akut giftiga men har däremot subletal påverkan i låga doser.Fluoxetine is the active substance in many selective serotonin reuptake inhibitive pharmaceuticals that currently enters surface waters. The substance has been shown to affect behaviors of water living organism such as fish, molluscs and crustaceans by making them less cautious. This study investigated the acute (on wild caught individuals) and chronic (on lab reared individuals) effects of fluoxetine on the antipredator behavior of Asellus aquaticus for three concentrations; 0,3 and 30 ng L-1. Three tests were used to determine the effects: (1) time to leave a shelter, (2) spontaneous activity and (3) escape behavior under predation risk. Few statistically significant effects of fluoxetine on A. aquaticus were found. However, individuals exposed to fluoxetine had a significantly shorter (30 %) escape period. Besides this main effect of fluoxetine, significant interactions between the two groups and fluoxetine were also found. When exposed to the highest concentration wild caught individuals increased their spontaneous activity (38 % more stops and 49 % more movement), while lab reared individuals reduced their activity (43 % fewer stop and 37 % less movement). Furthermore, non-exposed individuals from the two groups behaved significantly different in all the tests. It is likely that the differences in behavior occurred due to environmental effects of laboratory rearing, although altered gene frequencies cannot be excluded. This study emphasizes the need for development of methods for more chronic testing of pharmaceuticals, especially considering that pharmaceuticals are seldom acutely toxic but often has sub lethal effects in low doses.
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Brown, Allison. "Variation in the Flexibility of Potential Anti-Predator Behaviours among Larval Damselflies." Thesis, 2013. http://hdl.handle.net/10214/5426.
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Heterogeneous environments play an important role in the evolution of traits when selection is diversifying between different conditions. One response is the capacity of individuals to beneficially adjust their phenotype to local conditions, such as different predators. In larval Enallagma damselflies, diversifying selection from predatory dragonfly larvae or predatory fish favours opposing traits, respectively high or low levels of activity, and so appears to drive the adaptive divergence of anti-predator specialists. However, little work has addressed: i) if anti-predator generalist species exist; ii) if anti-predator generalist species express adaptive flexible behaviour; iii) if adaptive flexible behaviour is influenced by prior experience with predators. I compared individual larval behaviour in the presence of fish, dragonfly larvae, or no predators, in four Enallagma species groups from ponds with and without fish predators. Ecological distributions suggest variation in degree of anti-predator generalization, and this was associated with increased responsiveness to predator treatment in the most likely ecological generalist. Responses to predators varied across different behaviours and sometimes were shaped by prior predation experience. Thus, a variety of adaptive strategies may have evolved to cope with heterogeneity in predation risk in larval damselflies.NSERC, OGS
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"EFFECTS OF EMBRYONIC EXPOSURE TO PREDATOR CUES ON PRE- AND POST-HATCHING ANTIPREDATOR BEHAVIOUR IN COMMON CUTTLEFISH (SEPIA OFFICINALIS)." Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-12-1854.
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Since neonates are often the age-class most susceptible to predation, there should be strong selective pressure on prey for the early development of successful antipredator behaviour. The ability to assess predation risk as early as the embryonic stages may increase an individual’s survival, as it would allow young individuals to be better adapted to current predation risk, since present conditions are often a good short-term indicator of future conditions. I exposed embryonic cuttlefish (Sepia officinalis) to the odour of a predator and tested both the responses of the embryos to this stimulus, and the latent effects of both long (approximately 3 weeks)- and short (a few days)- exposure on the behaviour of newly-hatched juveniles, in particular the efficiency of cryptic behaviour on uniform and sandy substrates. Exposure to novel odours, whether they were predators or non-predators, increased the ventilation rate of embryos. This may be adaptive, because it helps an individual survive first encounters with unknown potential dangers before they have opportunity to collect information about a novel stimulus. Long-term exposure to predator odour increased the camouflage efficiencies of juveniles on uniform substrates. On sandy substrate, the exposure did not affect camouflage, but increased the extent of sand digging behaviour. Juveniles were also larger in size at hatching when exposed to predators compared to those that were not. These results were not seen in individuals with only short-term exposure to predator. Short-term exposure also had no effect on camouflage efficiencies on uniform or sandy substrates, or on sand digging behaviour. The results of my thesis indicate that high predation risk during embryonic development induces behavioural and morphological changes in camouflage expression and body size in cuttlefish hatchlings. The behavioural plasticity may provide survival benefits for newly hatched individuals, but may come at a cost in terms of body size. Such behavioural and morphological plasticity may have an impact on predator-prey dynamics and organization of communities.
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Bell, Katherine. "Stress physiology and anti-predator behaviour in urban Northwestern Gartersnakes (Thamnophis ordinoides)." Thesis, 2013. http://hdl.handle.net/1828/5122.
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Over 50% of the world’s human population resides in urban centres, and this is expected to increase as the global human population grows and people migrate from non-urban to urban centres. Concentrated in these urban areas are anthropogenic disturbances that impose additional challenges on wildlife compared to their non-urban counterparts. These challenges can be stress provoking. Through the release of corticosterone (CORT) reptiles can adapt to these stressors, physiologically and behaviourally, both in the short- and long-term. To investigate the relationships between stress activation and defensive tactics in wild urban Northwestern Gartersnakes (Thamnophis ordinoides) I conducted visual encounter surveys, along edge-focused transects, following a semi-constrained random sampling method. I sampled snakes at five sites, each with a different level of anthropogenic disturbance, in the Greater Victoria Area, BC. I sampled blood, observed anti-predator behaviour, and collected data on characteristics of snakes. The most disturbed site (with the most people, pets, and natural predators) also had the most snakes: those snakes also had highest H:L values (a proxy of CORT) in their blood compared to the other populations. Nevertheless, none of the snakes had H:L values that indicated chronic stress. Stress physiology was not correlated with anti-predator behaviour. More important to anti-predator behaviour was the size, sex/reproductive condition, and cloacal temperature of snakes. Although anthropogenic development can reduce habitat quality for some reptiles, Northwestern Gartersnakes coexist with recreationists at many sites in the District of Saanich. A multi-disciplinary approach is of paramount importance to understand the full effect of anthropogenic influences on wildlife.Graduate
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Manassa, Rachel Penelope. "Social learning and its role in anti-predator behaviour by coral reef fishes." Thesis, 2013. https://researchonline.jcu.edu.au/40088/1/40088-manassa-2013-thesis.pdf.
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The lifetime fitness of a prey is directly affected by its ability to detect and avoid predators. However, predator avoidance is costly as it reduces the time and energy available for other fitness related activities. Prey must therefore continually modify and update their behaviour towards predators through the process of learning. As a variety of information sources are available to individuals at any one time, knowledge on how animals make decisions is essential for our understanding of animal behaviour. Often an individual's decisions are affected by the presence of others. This thesis investigates the importance of social interactions to the assessment of predation risk, using coral reef fish as model organisms.
Ignoring accurate information on predation risk could lead to death; therefore prey individuals are likely to have evolved the ability to incorporate multiple sources of information, extract important components and respond accordingly. Chapter 2 explored how juvenile reef fish incorporate multiple sources of information to mediate their risk response and how information sources are prioritised. Naïve anemonefish (Amphiprion percula) were exposed to damage-released chemical cues of conspecifics and closely related congenerics (Amphiprion melanopus), along with additional control cues in the presence and absence of a shoal (conspecifics, congenerics or no shoal). A. percula responded with anti-predator behaviour to the chemical cues from both conspecifics and congenerics, with visual cues dramatically influencing the response elicited. These findings emphasise the ability of coral reef fish to incorporate multiple sources of information into their decision making process, allowing individuals to reduce any uncertainty.
Information can be gained through the process of social learning, where less experienced individuals learn from observing and/or interacting with experienced group members. Chapter 3 examined the role of social learning in predator recognition in relation to the survival of newly settled juvenile reef fish. Naïve damselfish (Pomacentrus wardi) were tested for their ability to socially transmit the recognition of a predator odour to conspecifics. Along with this, the study also determined whether there was a difference in the rate of survival between individuals that directly learnt the predator odour and those who acquired the information through social learning. Results showed that P. wardi are capable of using social learning to transmit information, with the survival outcome not significantly different from those who directly experienced predator conditioning. As such, this study demonstrates that experience plays a vital role in the outcome of predator-prey interactions, with social learning improving the ability of prey to avoid and/or escape predation.
In a natural setting social learning is likely to occur between more than 2 individuals, as such investigating the effect that group size has on the learning process is vital. Chapter 4 determined the effect of group size on the ability of the damselfish, Pomacentrus amboinensis to socially learn to recognise an unknown predator. Specifically, individuals were tested to see if social learning occurred when the number of less experienced individuals (observers) was increased from 1 to 5, and if the intensity of the anti-predator response differed depending on the size of the group. Regardless of group size, P. amboinensis individuals were capable of socially transmitting the recognition of an unknown predator to conspecifics, with the intensity of the response not significantly different between predator-naïve observers who learnt when they were alone compared to when they were one of five observers. Social learning is therefore an important method of acquiring information about predators in aquatic ecosystems, ensuring that the value of the information is transferred in its entirety.
Along with intraspecific social learning (transmission of information between conspecifics), interspecific social learning (transmission of information between species) is likely to be commonplace in biologically complex environments such as coral reefs. Therefore, Chapter 5 tested if social learning of predator recognition occurs among three species of coral reef fishes. Individuals of both Pomacentrus moluccensis and Apogon trimaculatus were tested for their ability to socially learn from P. wardi. Based on a single conditioning event, individuals of both species were able to learn a predator's identity from experienced P. wardi individuals. This ability to utilise social information from heterospecifics is likely to confer a significant survival advantage, especially for coral reef fishes as they are faced with constant and unpredictable predation pressures.
Predation pressure is highest during critical life history transitions where the suite of predators one encounters is both diverse and variable. For coral reef fishes, one of the most significant transitions occurs following a planktonic larval stage; settlement into a benthic life. As this stage occurs at night, Chapter 6 explored whether social learning of predator recognition can occur in total darkness. Results demonstrated that predator-naïve anemonefish, A. percula, are capable of socially learning to recognise a novel predator when paired with a predator-experienced conspecific under both light and dark conditions. These results show that visual cues are unlikely to be the sole sensory system responsible, therefore, the study also tested whether when threatened individuals release chemical cues known as disturbance cues into the water. A. percula did release disturbance cues following exposure to predator odour; however these cues did not facilitate learnt recognition. It is likely that another sensory modality, possibly mechano-sensory in origin, is responsible for information transfer in the dark, with this study highlighting the diversity of sensory cues available to coral reef fishes.
This thesis demonstrates the use of social learning as an anti-predator mechanism, highlighting the importance of olfactory cues for predator recognition in biologically complex ecosystems. Obtaining accurate information on local predator identities is essential to the decision process of individuals, with the choices made ultimately determining the outcome of predator-prey interactions. Furthermore, this study demonstrates the speed with which information can spread through a local prey population without a dilution of importance; highlighting the role of social interactions in the cognitive processes of coral reef fishes.
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"Learning to recognize and generalize the sight of predators and non-predators : does turbidity impair recognition?" Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-02-921.
Full textAbstract:
To be successful, individuals that are susceptible to predation have to optimize the trade-offs between predator avoidance and other fitness related activities such as foraging or reproduction. One challenge for prey is to identify which species pose a threat and should be avoided, and which species should be ignored. The goal of this study was to investigate whether minnows can generalize recognition of predators and non-predators using visual cues. I conducted experiments in both clear and turbid conditions to test whether the level of turbidity affects the quality of visual information available to the prey and hence the ability of prey to generalize. Latent inhibition and learned irrelevance are mechanisms of learning that can be used by prey to recognize stimuli as non-risky. Repeated exposure to an unknown stimulus in the absence of risk leads to the stimulus being categorized as non-risky. Fathead minnows were pre-exposed to the sight of brook trout or control water to provide minnows the opportunity to learn to recognize the trout as a non-predator. Following this the fish were conditioned with alarm cues (AC) to the sight of each predator paired and then their responses to the sight of brook trout, rainbow trout, and yellow perch were tested either in clear or turbid water. In clear water, minnows conditioned to recognize one of the trout species generalized their response to the other species. However, when the minnows were pre-exposed to the sight of a brook trout, they were inhibited from subsequently recognizing the sight of brook trout as threat and generalized this non-predator recognition to the sight of rainbow trout but not to yellow perch.
In turbid water, however, minnows that were pre-exposed to the sight of brook trout had impaired responses to all predators while those pre-exposed to water showed an intermediate intensity anti-predator response toward each predator. Overall, my results demonstrate that minnows were able to distinguish between predators and non-predators in the clear environment but turbidity influences the visual information used by minnows and hence impaired the minnow’s ability to recognize and generalize the sight of predators and non-predator species.
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Huang, Sheng-Chih, and 黃聖智. "Investigation on byssus secretion for anti-predator behavior of Perna viridis（Linnaeus, 1758）." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/16174966003655695369.
Full textAbstract:
碩士國立高雄師範大學
生物科技系
100
This research is focused on the behavioral model of Perna viridis byssus in anti- predatory responses. Field experiments were conducted in Hsingda harbor to investigate P. viridis byssus response on the survival condition of adjacent conspecific and heterospecific feeding habits; and P. viridis byssus in anti- predatory responses on the sympatry, allopatry, survival condition, hunting habbits, differences in body size and morphology of predator were also explored. Chi-square test was used to identify the response variations on P. viridis byssus ( trap no escape, trap escape, no trap ) , and differences between the numerical abundance and diameter of byssal thread were analyzed. The results found that the response was not significant difference between the survival and death of adjacent species; however, significant difference with sympatric, filter feeders, such as Crassostrea angulata, Thais clavigera and Thais bufo, was identified. The results also showed that the secretion of byssus by P. viridis form a anti-predator responses to competitive filter feeders and specific drill hole carnivore.
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Hartley, Fraser Andrew. "Fear of fishers: anti-predator behaviour of coral reef fish and its relevance to fisheries management and conservation." Thesis, 2013. https://researchonline.jcu.edu.au/32003/1/32003_Hartley_2013_thesis.pdf.
Full textAbstract:
Responding appropriately to predators is essential for prey animals to maximise fitness and survival. Non-lethal predator-prey dynamics can have large effects on how animals use and perceive their environment. The understanding of predator escape behaviour in animals can play an important role in conservation and management, with implications for human/wildlife interactions, particularly hunting and tourism. In this thesis I use coral reef fish as model organisms to examine our existing knowledge of factors influencing prey flight response in the context of marine ecosystems. I go on to examine how fishing and protection from fishing influences the flight behaviour of fishery target coral reef fishes through the use of no-take reserves (NTRs) and periodically harvested closures (PHCs).
Flight initiation distance (FID - how close a predator can get to an animal before it flees) is widely used when investigating how prey animals respond to predation, and has been utilised in systems where humans are predators or otherwise disturb wildlife (e.g., through tourism such as bird watching). However, the use of FID in the marine realm prior to this thesis was limited. Studies investigating FID vary in methodology and many of the potential confounding effects inherent to in-water estimation of FID have yet to be investigated. In Chapter 2, I compared the relative effects of spear guns, dive gear (SCUBA vs. free diving), observer bias and protection from fishing on estimates of FID. FID in areas protected from fishing was, on average, 141 cm lower than in fished areas, with no difference found between treatments for either dive gear or speargun. Management status explained 60% of the variation in FID estimates, while differences between observers only accounted for 4%. Size was highly significant, with larger fishes being associated with greater FID in every treatment. These findings imply that fishes use only limited predator attributes as cues for flight, and that the response of fishes to these attributes is amplified in areas of higher predation risk.
In Chapter 3 I examined how FID changed across a range of families and fishing pressures on coral reefs in Papua New Guinea. I surveyed FID, fish size, group size and pre-flight behaviour of two families commonly targeted by spearfishers - Acanthuridae and Scaridae - and four families that were less common in the spearfish catch – Balistidae, Lutjanidae, Mullidae and Serranidae (groupers) across four levels of fishing pressure. Increases in fishing pressure were associated with increases in FID for Acanthuridae, Balistidae, Mullidae, and Scaridae, while FID of Lutjanidae and Serranidae showed no relationship with fishing pressure. Notably, mean FID of Lutjanids was greater than the mean effective range (MER) of spear guns, while the mean FID of Serranids was lower than other families. Larger individuals tended to flee earlier, particularly at moderate or high fishing pressures, while group size and pre-flight behaviour differed between families, but showed low concordance with fishing pressure. These findings indicate that the relationship between size and FID of coral reef fishes is more complex than has previously been presented, and that an interaction between predation experienced by fish families and traits such as territoriality or trophic level, may be important in determining FID.
One of the benefits expected from NTRs is spillover of adult biomass to adjacent fishery grounds, through density dependent export or random movement of fishes across NTR borders. Fishes with little experience of predation may transport non-wary behaviours across the borders of marine reserves, resulting in a gradient of increasing FID with distance from the reserve border. In Chapter 4 I examined FID and biomass of Acanthuridae and Scaridae, and one non-target family (Chaetodontidae) across the borders of three NTRs and three control borders within fished areas in the Philippines. FID only increased significantly with distance from the NTR centre for the two fishery families at NTRs, and remained below FID recorded in fished areas until 140 m outside the NTR, significantly further than spillover of biomass. These reductions in FID are likely to lead to increased catchability of fishes near NTRs. While this may increase local support for management, changes in catchability may give rise to inaccurate estimates of NTR effects on fish biomass and abundance.
Across the South Pacific, PHCs are often utilised in place of NTRs, with the specific aim of taming fishes to increase catchability and produce high yields during harvests. Using a before-after-control-impact-pair design, in Chapter 5 I investigated whether PHCs in Vanuatu had similar effects on fish FID and biomass as NTRs, and the effects of a single harvest. Catch per unit effort was higher during the harvest than for regular fishing, and this was linked to FID of Acanthuridae being lower than MER of spear guns in PHCs. Acanthuridae also increased as a proportion of the catch, and showed substantially lower biomass in PHCs than NTRs, even with no detectable effect of the harvest on UVC estimates of biomass. The effects of PHCs are attuned to the expectations of local communities. However, differences in the magnitude of behavioural changes between fishery-target families may result in contrasting outcomes of PHC management regimes.
In Chapter 6 I tested whether predictions of increased FID with increased predation risk, size of individual and availability of refuge were consistent across a broad range of fishing pressures around protected areas and inside fished areas. I included FID of fishes from the Chagos Archipelago, which is a completely unfished population, and FID from areas in Vanuatu, Philippines and Papua New Guinea. FID in fished areas was consistently higher than protected areas across the spectrum of fishing pressure. Both in fished areas and protected areas, fishing pressure had the most support explaining FID, followed by fish size then refuge availability. Life-history stage was not a significant predictor. These results show that fishing effects such as increases in wariness can be imported into marine reserves, and supports predictions of increases in FID with increased predation risk and size (as a loose proxy for reproductive values).
Previous studies have shown increases in FID with hunting, a result confirmed here for coral reef fishes. Experience of predation and some prey conditional and environmental factors can all have significant influences on FID. In contrast, little evidence was found for other factors such as predator attributes or group size. In general, I found that the level of predation risk in the environment tends to have the largest effect on FID (Chapters 2), while fish family, prey size and environmental variables had small but significant effects (Chapters 3, 6). These results have important implications for management, showing that changes in fish behaviour can positively influence fishing on during the harvest of PHCs (Chapter 5), and around the borders of NTRs (Chapter 6), both of which may help increase stakeholder support for management. Temporary changes in behaviour caused by management may increase the susceptibility of fishes to fishing gears, and reduce the impacts of protection. Furthermore, borders of NTRs are porous to behaviour, and fishery mediated behavioural changes may be ubiquitous within smaller NTRS within heavily fished seascapes (Chapter 6).
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Chen, Guan-Hua, and 陳冠樺. "Formosan Macaque (Maraca cyclopes) anti-predator behaviors in response to mimicked or real Mountain Hawk Eagle (Nisaetus nipalensis) calls." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/79171915293423102985.
Full textAbstract:
碩士國立屏東科技大學
野生動物保育研究所
100
Primates have different warning responses for different predators. Can primates differentiate between birds-mimicking calls or the actual calls of natural predators? In Taiwan, Mountain hawks eagle (Nisaetus nipalensis), the the largest diurnal forest raptor, is a predator to Formosan macaques (Macaca cyclopis), and the bird’s call was frequently imitated by Eurasian Jays (Garrulus glandarius). I did the playback of mimicked calls by the jays, that of the hawk eagle and Crested Serpent Eagle (Spilornis cheela) in regions with or without the distribution of the hawk eagle to see whether macaques could differeciate among them. Crested serpent eagle is widely distributed in Taiwan, whose call is not strange to the macaque, and therefore was used for control. My study sites were located at Tahanshan and Shoushan, with and without the hawk eagle existence, respectively. I conducted the playback of one call type to each macaque flock encountered on the trail, and call type was used in the order of hawk eagle call, Crested serpent eagle call and minicked call. Results showed that Tahanshan macaques showed more anti-predator behaviors than in Shoushan to Mountain Hawk Eagle calls and minicked calls as well (NT=20, NS=17, t=12.735, df=35, *** P < 0.001). Formosan macaque group vigilance rate were significantly different between both with and without Mountain hawk eagle sites when broadcasting Mountain hawk eagle calls playback (NT=20, NS=17, t=12.735, df=35, *** P < 0.001) and jay imitate eagle calls (NT=20, NS=17, t=2.705, df=35, *** P < 0.001). But when I broadcasted serpent eagle call, macaques showed the anti-predator behaviors but vigilance rate were not significantly different between the two sites (NT=20, NS=17, t=0.920, df=35, P =0.06). Macaques showed the most fiercest anti-predator behaviors and response to hawk eagle call in Tahanshan. In conclusion, macaques could be fooled by the minicked call occassionally, and anti-predator behavior of macaque was affected by whether the hawk eagle existed or not, and this tended to be a learning behavior.
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"Life-skills training for juvenile lake sturgeon (Acipenser fulvescens)." Thesis, 2015. http://hdl.handle.net/10388/ETD-2015-01-1928.
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Hatchery supplementation of declining fish populations is used for increasing year-class strength, particularly when fish are released with knowledge of local predators. The ability of young-of-the-year lake sturgeon (Acipenser fulvescens) to avoid predation, as well as their vulnerability to predation, remains undocumented. The objective of my thesis was to determine: 1) whether hatchery-reared, predator-naive juvenile sturgeon would respond to alarm cues from injured conspecific cues, a reliable indicator of predation risk in other fishes; and 2) if sturgeon would learn to identify unknown predators through a Pavlovian-like conditioning with conspecific alarm cues. Releaser-induced recognition learning is a variant of Pavlovian learning in which recognition of a previously neutral stimulus is acquired through the experience of pairing a behaviourally active releasing stimulus and a novel stimulus. Sturgeon were initially conditioned using a behaviourally active stimulus of sturgeon alarm cue, paired with a behaviourally neutral stimulus of novel northern pike (Esox lucius) odour, or were pseudo-conditioned with distilled water paired with pike odour. Following conditioning, sturgeon were tested for recognition of the predator odour 24 hours later. The first population of fish (Rainy River) showed a dramatic antipredator response to alarm cues from the skin of conspecifics, but failed to exhibit learning of a novel predator through conditioning with alarm cues obtained from the skin of conspecifics. However, when Rainy River fish were conditioned with alarm cues from the whole body of conspecifics, they showed strong learning of the predator. Conditioning Wolf River fish to recognize predators with whole body extract had no effect on response to predator odours. However, when the fish were conditioned multiple times there was evidence of predator learning. These results highlight potential opportunities and limitation to life-skill training of artificially reared sturgeon for future conservation initiatives.
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Bayandonoi, Gantulga. "Cooperative breeding and anti-predator strategies of the azure-winged magpie (Cyanopica cyanus Pallas, 1776) in northern Mongolia." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-87B9-3.
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Visscher, Darcy Richard. "Trade-offs between risk and reward at multiple scales a state-dependent approach /." Phd thesis, 2010. http://hdl.handle.net/10048/1082.
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Thesis (Ph. D.)--University of Alberta, 2010.Title from pdf file main screen (viewed on July 7, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Biological Sciences, University of Alberta. Includes bibliographical references.
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NĚMEC, Michal. "Jak ťuhýk obecný (Lanius collurio) rozpoznává nepřátele." Doctoral thesis, 2015. http://www.nusl.cz/ntk/nusl-187420.
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This study investigates two questions about anti-predator behaviour of the red-backed shrike. 1) Is the red-backed shrike able to assess the differing dangers represented by various types or species of predators? 2) How does the red-backed shrike recognize the predator? We found, that the red-backed shrike (Lanius collurio) adjusts its anti-predator behaviour by assessing the potential threat to themselves from different predator species and by assessing the chance of a successful attack. Further, we found that the presence of general raptor salient features is absolutely necessary for proper categorisation of the intruder as a predator, whereas the natural species-specific colouration in itself is an insufficient cue.
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Ellwanger, Nicholas. "Behavioural strategies of the ring-tailed lemur (Lemur catta) in a sub-desert spiny forest habitat at Berenty Reserve, Madagascar." Thesis, 2007. http://hdl.handle.net/1828/303.
Full textAbstract:
In an effort to better understand primate behavioural flexibility and responses to low-biomass habitats, behavioural patterns of ring-tailed lemurs (Lemur catta) living in a xerophytic spiny forest habitat in southern Madagascar were examined. Behavioural data were collected over two months on two separate groups living in two distinctly different habitats: a sub-desert spiny forest and a riverine gallery forest. Data on the following behavioural categories integral to primate sociality were collected: time allocation, anti-predator vigilance, predator sensitive foraging, feeding competition, and affiliative behaviour. L. catta living in the spiny forest habitat differed significantly in many behavioural patterns when compared to L. catta living in the gallery forest. I suggest that the ability to successfully alter behavioural strategies to varying ecological conditions allows ring-tailed lemurs to occupy low biomass habitats which are uninhabitable to nearly all other primate species in Madagascar. Lemur catta evolution, behavioural flexibility, and conservation will be discussed.
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Hollings, T. "Ecological effects of disease-induced apex predator decline." Thesis, 2013. https://eprints.utas.edu.au/17084/2/whole-Hollings-thesis-exc-pub-mat.pdf.
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The global extirpation of the world’s apex predator fauna is consistently highlighting their important functional role in preserving biodiversity and maintaining ecosystem resilience. Apex predator declines and extinctions are promoting more invasive and homogenised ecosystem states, linked with secondary species extinctions, changes to community composition, and redefined carnivore guilds. In taxonomically and geographically diverse ecosystems devoid of apex predators similar general patterns expressed in community dynamics are emerging, such as mesopredator release, yet the magnitude and significance of the effects are driven by their context.
The Tasmanian devil (Sarcophilus harrisii) is the largest extant marsupial carnivore and is facing the real threat of disease induced extinction in the wild from a consistently fatal transmissible cancer, devil facial tumour disease (DFTD). The devil is now effectively the apex mammalian predator in Tasmanian ecosystems following the extinction of the thylacine (Thylacinus cynocephalus) but DFTD is threatening its ecological role in the environment. Since the disease arose in the early to mid 1990s devil populations have suffered declines in excess of 95% in long-term disease areas, and it has infected more that 75% of their current geographic range. Tasmania retains the most intact guild of marsupial carnivores in Australia and maintains healthy populations of many native mammal and bird species that are extinct or threatened on mainland Australia. The loss of Tasmanian devils over large tracts of Tasmania is of tremendous conservation concern for native biodiversity and community resilience. This study provides the first assessment of the ecosystem effects of Tasmanian devil decline and aims to determine overarching effects of the loss of an ecologically functional devil population on terrestrial mammalian fauna. Within the scope of this thesis, broad concepts encompassing abundance, behaviour and disease ecology of native and introduced species are assessed within four discrete projects. I utilised complimentary approaches with the benefit of this unique large scale natural experiment to assess common theories as well as considering less widely examined concepts which may be pertinent to global apex predator demise. First, using a state-wide spotlighting database which pre-dates DFTD by more than a decade, I evaluated the mesopredator release hypothesis (MRH) and the extent to which mesopredators are regulated by top-down or bottom-up environmental processes. Second, I conducted a rapid snapshot survey across a large spatial extent encompassing different devil densities to assess changes to community composition, invasive system states and the cascading effects of mesopredator release on populations of their prey. Third, I measured risk-sensitive behaviour of the common brushtail possum, a species regularly preyed upon by Tasmanian devils, employing a ‘giving up densities’ approach across a DFTD arrival gradient, which represents a proxy for devil population decline over time. Finally, following the evidence for mesopredator release of feral cats, I assessed whether there was potential for increased disease transmission of Toxoplasma gondii, a parasite whose only known definitive hosts are members of the Felid family but that can infect all warm-blooded mammals.
This study provided several lines of evidence for a shifting ecosystem state and increasing threats to the persistence of native biodiversity in response to declining devil populations. Less diverse communities and a strong tendency towards more invasive system states were characteristic of areas with long-term devil decline. Native and introduced mammals responded differently to devil decline, and the direction of the response for species of each origin was consistent across different trophic levels. I found strong evidence for mesopredator release of the invasive feral cat (Felis catus) in response to devil decline and a concomitant decline and changing activity times in the much smaller native eastern quoll (Dasyurus viverrinus), suggesting that they may be indirectly protected by devils. Despite the comparable size and prey range of native spotted-tailed quolls (Dasyurus maculatus) to feral cats, there was no evidence of a similar response, notwithstanding some evidence for different activity times across different devil densities. The magnitude of the responses of mesopredators to declining devil populations was significantly affected by environmental variables. In anthropogenically dominated landscapes bottom-up control appears to be the principal regulating force, and in less disturbed areas top-down control is stronger. There was evidence for an increasingly invasive state, represented by a significantly higher proportion of activity of feral cats and introduced small mammals, which appeared to be affecting native prey species. Small- and medium-sized native species within the prey size range of large mesopredators showed population declines analogous to the declines observed in devil populations and also evidence for increased predation pressure, indicating that apex predator loss in Tasmania is threatening native biodiversity.
There was evidence of behavioural responses in prey species to the decline in devil numbers. Using the giving up densities approach, I found evidence that the predominantly arboreal brushtail possum (Trichosurus vulpecula), a common prey item of devils, has changed its anti-predator behaviours and has increased its ground foraging activity in response to declining devil populations, whilst maintaining vigilant behaviours appropriate for the avoidance of other predator species. Behavioural responses have the potential to initiate a trophic cascade if changes in behaviour translate into increased fitness and reproductive output.
Some native species are at risk from higher feral cat densities not only from increasing predation pressure but also from potentially amplified transmission of the Toxoplasma parasite. Australian native marsupials may be particularly susceptible to acute Toxoplasma, a consequence likely attributable to a lack of co-evolution. I found tentative support for higher prevalence rates in areas with higher cat densities and also a strong link to increased susceptibility in native species at higher trophic levels. There was also some suggestion for reduced behavioural reactions in infected individuals, with the potential to increase predation rates. This was among the first research that has investigated changing disease dynamics in response to mesopredator release, and represents an important and novel step towards more wide-ranging research of the effects of apex predator loss on biodiversity.
The combined results, derived from empirical approaches, provide compelling evidence that diverse and complex changes are occurring in Tasmania’s fauna communities following apex predator decline. The evidence is indicative of extensive and far-reaching consequences in the Tasmanian ecosystem, threatening native biodiversity and promoting alternative ecosystem states. The lessons learned from applying existing community ecology theories and approaches to this unique large scale natural experiment are applicable to other ecosystems confronted with apex predator loss and highlight the importance of a multifaceted and comprehensive approach to apex predator studies.