Academic literature on the topic 'Intersexual interactions'

Differences in reproductive investment between males and females can be a basis for both intra- and inter-sexual conflict. In a series of laboratory experiments, I staged intra- and inter-sexual contests for food between pairs of adult ground skinks (Scincella lateralis). Males were significantly more aggressive than females. Size asymmetry between contestants significantly affected intrasexual behavior between females, as smaller individuals exhibited avoidance behaviors more frequently than larger individuals. Aggression was more prevalent in intersexual contests than in intrasexual contests, and males bit females significantly more often than females bit males. Females captured significantly fewer prey in the presence of a male than in control tests, but showed more avoidance behaviors in intersexual contests than did males. These results suggest that intersexual conflict may be important in social interactions in ground skinks, particularly with respect to spatial distribution.

The difficulty of observing the behaviour of cryptic, nocturnal carnivorous marsupials (Dasyuridae) in the wild has created a reliance on laboratory studies for the analysis of social interactions. Behavioural data on wild Phascogale tapoatafa suggest that previous interpretations may be biased by laboratory confinement. The play of juvenile P. tapoatafa entailed brief, non-contact chases, which apparently provide social practice prior to the solitary, post-dispersal life of adults. Interactions between wild adults very rarely included physical contact. Most encounters (63%) comprised chases, of which only female-female interactions commonly displaced the chased animal more than 3 m. Wild females readily deterred males from approaching closely by vocal threatening, even during the peak of the breeding season, so that forced copulation (as reported in captive dasyurids) was unlikely. Scent-presentation experiments suggested that sternal marking by males was intersexual communication, and may serve, along with intersexual chases, to familiarise females with future mates.

AbstractSocial interactions of conspecifics are a function of complex relationships involving resource defense, antipredatory tactics, and mate acquisition. Consequently, individuals often associate non-randomly with conspecifics in their habitats, with spatial distributions of adults ranging from territorial spacing to aggregations. Site tenacity and cohabitation patterns have been well studied in many species of terrestrial salamander; however, less is understood about these behaviors in aquatic species. We examined the cohabitation patterns of intrasexual and intersexual pairs of the federally threatened, paedomorphic San Marcos salamander (Eurycea nana) under artificial shelters in a laboratory setting over a 20-day period. We found that intrasexual female pairs and intersexual pairs were found cohabiting more often than intrasexual male pairs. We also assessed site tenacity by examining shelter affinity and found that both males and females inhabited one of the two shelters more often than expected from random habitation, regardless of whether they were in intersexual or intrasexual pairings. Our results indicate that although both sexes of Eurycea nana exhibit site affinity, the sex of individuals is an important determinant of cohabitation patterns.

Abstract Individuals avoid potential competitors accessing mates during reproductive periods staying close to the mate and chasing same-sex intruders. We studied intersexual relationships and the effect of intruders of each sex in male-female pairs of Chalcides viridanus. We analysed: (1) behaviour patterns of each pair member and the time they spent together during three successive days in March, April and May; and (2) interactions of intruder-resident of the same sex, during each of the three months. Sexual and monthly differences appeared in intersexual behaviour as the breeding season progressed. In each month, time together was significantly larger on the third trial day than in the two previous days but did not significantly change between months. Sexes did not significantly differ in intruder-resident behaviours, but male aggressive interactions were significantly larger in May. Intruder females performed higher frequencies of non-agonistic behaviours than residents. We discuss all these results considering the predictions of mate guarding hypothesis.

Recent experiments indicate that male preferential harassment of high-quality females reduces the variance in female fitness, thereby weakening natural selection through females and hampering adaptation and purging. We propose that this phenomenon, which results from a combination of male choice and male-induced harm, should be mediated by the physical environment in which intersexual interactions occur. Using Drosophila melanogaster , we examined intersexual interactions in small and simple (standard fly vials) versus slightly more realistic (small cages with spatial structure) environments. We show that in these more realistic environments, sexual interactions are less frequent, are no longer biased towards high-quality females, and that overall male harm is reduced. Next, we examine the selective advantage of high- over low-quality females while manipulating the opportunity for male choice. Male choice weakens the viability advantage of high-quality females in the simple environment, consistent with previous work, but strengthens selection on females in the more realistic environment. Laboratory studies in simple environments have strongly shaped our understanding of sexual conflict but may provide biased insight. Our results suggest that the physical environment plays a key role in the evolutionary consequences of sexual interactions and ultimately the alignment of natural and sexual selection.

In many species, male animals produce costly signals to attract females. Intersexual indicator theories propose that these signals are indicative of male quality, whereas individual recognition models are based on the idea that male signals are used primarily to allow for individual discrimination. These two types of models make differing predictions about the nature of male signals. In particular, these models’ predictions differ in the information about a male’s quality that will be included in his signal, the frequency distributions of male signals in a population, and the ways in which the different traits that make up a signal will covary. Calls from the Australian frog Litoria chloris were tested for consistency with the predictions of intersexual indicator models and individual recognition models. The calls were found to contain minimal information on male quality, and the covariance between different signal traits was consistent with the individual recognition models. However, the frequency distributions of male signal traits agreed with intersexual indicator models. In addition, this study found evidence that the information content of calls may instead mediate intrasexual interactions, although more research is required to determine if this is the case.

Although the behaviour of the Large Blue butterflies of the genus Phengaris (= Maculinea) is relatively well studied, most empirical data come from investigations of their dispersal and oviposition. Here, we assessed overall intersexual differences in resource use by tracking Phengaris teleius (Bergsträsser, 1779) individuals and recording the duration of their behaviours. Females were characterised by frequent, short flights, and devoted more time to resting and oviposition. Males engaged in numerous, but usually short interactions, and spent most of the time in flight exploring their surroundings for receptive females. Their average flight time was significantly longer compared to females. Average feeding time did not differ between the sexes but was shorter when butterflies were feeding on Sanguisorba officinalis L. Intraspecific interactions within P. teleius were three times longer than those with other insect species, and interactions between sexes were particularly long lasting. Significantly shorter interspecific interactions imply that butterflies can easily recognise conspecifics and differentiate between sexes, which offers obvious fitness benefits. Both sexes, but especially females, showed strong association with their larval host plant, and less so with other flowers of similar colour and shape. Females predominantly used their host plant for feeding, which possibly indicates neuro-sensory constraints towards this resource.

Pendant de nombreuses années, les femelles ont été décrites comme passives dans les interactions mâles-femelles et ont parfois été négligées dans les études sur les comportements reproducteurs et la communication animale. Pourtant, il est de plus en plus évident que les comportements des femelles influencent ceux des mâles et que les mâles peuvent ajuster leurs comportements de parades aux comportements des femelles. L’objectif principal de cette thèse est de mieux comprendre les signaux que les femelles émettent lors d’interactions avec un mâle dans un contexte de reproduction chez le canari domestique. L’ensemble de mes résultats montre tout d’abord que les femelles utilisent des signaux de parades visuels et acoustiques, c’est-à-dire des postures de sollicitation à l’accouplement et des trilles-spécifiques de femelles, comme une invitation à s’accoupler, mais qu’elles peuvent aussi les utiliser pour inciter le mâle à parader et l’aider à échantillonner la qualité de partenaires potentiels. D’autre part, ces deux signaux n’auraient pas la même efficacité selon le contexte d’émission. Ensuite, il semblerait que les signaux véhiculés par la modalité visuelle pourraient jouer un rôle plus important qu’on ne le pensait jusque-là dans les interactions intersexuelles chez cette espèce. Enfin, cette thèse a aussi pu apporter de nouveaux éléments concernant les préférences des femelles pour les chants de mâles et a montré que les méthodes utilisées en laboratoire pour tester les préférences des femelles étaient fiables et congruentes. Cette thèse permet de contribuer aux recherches grandissantes mettant en évidence le rôle important de la femelle dans les interactions intersexuelles
Much studies on reproduction and animal communication have considered the female as the passive sex; the role of the female during male-female interactions have often been overlooked. However, there is growing evidence that female behaviours can affect those of the males and that males can adjust their courtships to female behaviours. The aim of this thesis is to understand the signals produced by females during interactions with a male in a reproductive context in the domestic canary. Overall, my results show that females not only use their visual and acoustic signals, the copulation solicitation display and the female-specific trills, as an invitation to copulate but also to incite male to sing as an aid to sample potential mates. Then, these two signals could not have the same efficacy in different contexts of transmission. Moreover, the visual components of the communication seem to be more important than previously thought during intersexual interactions in this species. Finally, this thesis provides new elements about the female preferences for male songs and shows that methods used to test female preferences in laboratory are reliable and congruent. This thesis contributes to the growing number of researches showing that females play an active role in intersexual interactions

Competition between individuals of the same sex, intrasexual competition, has received much attention in males, mainly because such competition, which is primarily for mates (i.e. sexual selection), often selects for exaggerated, conspicuous ornaments and displays. In contrast, social interactions among females, particularly in common mating systems such as socially polygynous systems, have received limited attention. This is because sexual selection theory predicts lower variance in mating success in females than in males, and empirical work shows that females do not commonly display striking ornaments and conspicuous traits. However, recent reviews suggest that intrasexual competition in females can be widespread. Furthermore, while such competition is primarily for mates in males, females may compete not only for mates, but more commonly for resources related to enhancing offspring production and survival, including food, nesting sites, water, safety, etc. Reviews also indicate that intrasexual competition in females can have ecological and evolutionary consequences; and highlight the importance of studying intrasexual competition in females. In my thesis, I have focused on studying social interactions and intrasexual competition in females of a socially polygynous mating system. My study system, the Peninsular Rock Agama (Psammophilus dorsalis), is a sexually dimorphic lizard, in which, like most other polygynous systems, the brightly coloured and bigger males have received much attention, while our knowledge about the relatively duller and smaller females is limited. The nature of inter- and intra-sexual interactions can be broadly predicted by studying the space use of individuals and can be the first step towards understanding social interactions of a system. In my first chapter, I infer the interactions between and within sexes by studying their space use patterns, including variation in home range size, shifts in home ranges and intrasexual and intersexual overlaps in home range. I show that both males and females defend territories. Male territories are small in the non-mating season. However, in the mating season, male 13 territories expand and overlap multiple female and male territories. In contrast, female territories are small, exclude other females, do not change size throughout the year and are overlapped, on an average, by a single male’s territory. This suggests that P. dorsalis is a socially polygynous lizard and substantial intrasexual competition exists between females, which defend exclusive home ranges from other females throughout their lifetimes. Signalling is a key feature of intrasexual competition. Signals used in intersexual interactions are expected to be directed towards mate acquisition while those in intrasexual interactions in solitary territorial species like P. dorsalis are expected to influence mate and/or territory acquisition. Such effects on mate and territory acquisition are further likely to have an effect on the individual’s fitness. The extent to which females use signals and the functions of these signals in intrasexual competition are still not well understood. In my second chapter, I have studied patterns in signalling over the lifetime of females and the adaptiveness of these signals. That is, whether signals function to acquire resources in a sexual or non-sexual context and within the sexual context, how signals function in direct competition versus in indirect competition (i.e. mate attraction). Additionally, I have studied the strength of selection acting on these signals by studying correlation of signal use with proxies of fitness. My study shows that females use a complex signalling repertoire in which a set of well-defined signals are used exclusively in the mating context while others are likely used in competition in both the mating and non-mating contexts. In the mating season, different signals were used in direct competition and mate choice (indirect competition). I thus found evidence for multiple signals to be maintained in a population because distinct signals are directed towards different receivers. In spite of a variety of signals being used in intrasexual competition, I did not find any obvious correlation between signal uses and fitness proxies. However, it is important to note that I studied the relationship between signalling and measures of fitness like clutch size, tenure and perch quality. Maternity analysis using genetic methods might be important to examine the correlation between signalling levels and fitness. 14 Intrasexual interactions in the form of direct competition are widely studied in males because of the obvious physical aggression and conspicuous traits that appear to evolve under such selection, but have received minimal attention in females of a polygynous system. We suggest that though aggressive behaviours in females are not very commonly seen in the wild, competition in females should be strong. However, owing to the biological differences between the two sexes and higher costs of competition in females, the nature of intrasexual competition in females should be different from that in males. In my third chapter, I present hypotheses for strategies in direct intrasexual signalling and aggression in females and for sex differences in these strategies. I then test these hypotheses through observations and experiments. Results indicate that, as predicted, females use less conspicuous signals than males in broadcast signalling; however, they remarkably increase the intensity of signalling as the threat from a competitor increases. Though aggressive competitive events in the wild are generally uncommon, females strikingly increase aggression when the threat from a competitor is high. This suggests that perhaps because competition in females is more costly than in males, unlike males, they use low-key, inconspicuous signals in the normal signalling context; however, they are extremely sensitive to the level of threat, and ramp up their signalling and aggressive response at increased level of competitor threat, even more so than do males. Defending mutually exclusive territories can thus be a strategy used by females to avoid recurrent contests. My thesis highlights that intrasexual competition in females of polygynous systems can be substantially strong, however, cryptic. Females typically signal to compete directly as well as indirectly using well defined displays directed towards same and other sex individuals respectively. However, owing to the high costs of competition, females are extremely sensitive to the level of threat and strikingly increase signalling and aggression when level of threat is high, even more so than males. I suggest that female competition is difficult to detect because of its cryptic nature and experimental simulation of competitor threat might be key to studying intrasexual competition in females of a polygynous mating system