Academic literature on the topic 'Dasyurus Growth'

Growth and development of six captive litters of D. geoffroii were monitored at 1-5 day intervals from birth until they were left in dens at about 62-72 days of age. Two neonates were 4.4 mm long and weighed an average 11 mg. By the age of 63 days, juvenile weight had increased 1500-fold, to an average of 16.7 g. Growth of crown-rump length (from 0-40 days) and the square root of head width (from 8-65 days) is linear with respect to time. Wild D. geoffroii were first observed to be left in dens at the age of 62 days, soon after outgrowing the pouch. Wild and captive growth rates appear similar through the first half of pouch life. At older ages, wild litters generally grew more slowly than captive litters; wild litters belonging to thin mothers grew more slowly than litters with medium-weight mothers, which in turn grew more slowly than litters with fat mothers.

Observations on five species of rodents, vole (Microtus socialis), gerbil (Gerbillus dasyurus), jird (Meriones tristrami), dormouse (Eliomys melanurus) and jerboa (Jaculus orientalis), revealed that, during the period when their neonates share a matching morphology, they also share the same forms of quadruped locomotion (gaits). The order in which the different gaits develop is similar in all species, beginning with the basic gaits of lateral walk and trot. Gaits and body morphology do not undergo further changes in voles, whereas the other species incorporate more specialized gaits later in ontogeny, when the adult body morphology has been attained. Gerbils and jirds incorporate a bounding gait, dormice incorporate galloping and jerboas incorporate bipedal running. Species with more specialized locomotion thus undergo more developmental stages than those with less specialized locomotion. Except for the jerboa, the nesting period was roughly the same for all species, but those with more specialized locomotion exhibited earlier onset of the basic gaits as if condensing their development in order to reach the adult gait within the same nesting period. Consequently, the adult gait emerges approximately 10 days before the end of nesting, regardless of nesting duration. Since growth rate does not seem to account for the differences in morphology and onset of gaits, the heterochrony in the observed species probably stems from differences in the duration of growth, which seems to be the key factor in the diversion from the basic common morphology. The present results reconfirm the traditional generalities of functional morphology derived from cross-species comparisons. In addition, they provide another perspective by comparing form and function within the same individuals in the course of ontogeny.

Context Translocation is widely used to help avoid extinction of species from threatening processes. A fundamental objective of translocation is to establish self-sustaining populations; estimating demographic parameters is critical to assessing success of these programs and can also be used to support future management actions. Aims We estimated demographic parameters to evaluate the success of translocating the northern quoll Dasyurus hallucatus to two islands (Astell and Pobassoo), in response to the threat posed by the introduced cane toad Rhinella marina on the Australian mainland. Methods We used capture–mark–recapture methods to monitor both populations at regular intervals from initial release in 2003 until 2009 and a one-off survey in 2014. Key results Relative abundance (trap success) increased exponentially in the first 4 years, declined, and then stabilised in subsequent years. The population of female northern quolls on Astell Island peaked in 2006 with an estimate of 3640 (95% CI 3022–4257), and on Pobassoo Island the peak was 2007 with 617 (95% CI 531–703) females. In 2014 the population had decreased to 2193 (95% CI 1920–2467) on Astell and 451 (95% CI 359–543) on Pobassoo. Apparent survival and body condition decreased significantly following the population peak, possibly related to density dependence. Conclusion Both populations of northern quolls reached their regulation phase after going through establishment and growth phases, which included exceeding carrying capacity. The pattern was similar between the populations. Implications Increased survival and recruitment at threat-free translocation sites contributes to successful establishment of self-sustaining populations.

The red-tailed phascogale (Phascogale calura) is an endangered dasyurid species that has recently been brought into captivity in an effort to increase numbers before release back into the wild. As part of investigations into the reproductive biology of the species, information on the growth and development of young was collected throughout lactation from litters raised in three separate colonies. Growth curves for aging young throughout lactation and a timetable of developmental changes were constructed. While two colonies, with fourth- and fifth-generation captive animals, showed no significant difference in growth, animals from a third colony that had been wild caught before breeding displayed a slower rate of growth from 34 days of age. The pattern of development resembled that of other dasyurids, with young left in the nest from 44 days of age, fully furred by 78 days and weaned between 90 and 110 days. Captive phascogales invest heavily in their young, with litters weighing 380 ± 67% of maternal bodyweight at weaning.

Context Projecting the population trajectory of endangered species using models requires conservation practitioners to evaluate how variations in life history parameters may change a population’s viability. This is particularly important for species that occur as fragmented populations and whose densities are naturally low. Simulations may be used to identify conservation actions that have a higher likelihood of reducing a species’ extinction risk. Aims The aim was to apply population viability models to the northern quoll (Dasyurus hallucatus) under alternative scenarios. Methods The current (baseline) northern quoll demographic trajectories were evaluated using field-collected data derived from monitoring programs. The impact of alternative scenarios of mortality (for example, due to increased predation by introduced predators) and population supplementation (either from populations elsewhere or from captive breeding) on the viability of a northern quoll population was then determined. Key results Under current conditions, individual Pilbara populations of northern quoll are projected to persist for over 20 years. However, these populations are sensitive to extinction events. Population growth rate and local extinction risk were most sensitive to changes in juvenile mortality as low as 5% per annum. Increased mortality of the juvenile age cohort above current levels resulted in a projected decline in population size of 22–54%, with a moderate-to-high chance (20–96%) of local extinction within 20 years. Supplementing the population produced a moderate increase in quoll persistence over this time period. Conclusions Populations of northern quolls in the Pilbara, and potentially elsewhere in their range, are highly sensitive to even small perturbations in juvenile mortality rates. The continued persistence of quoll populations in fragmented refuges is characteristic of a species that functions as a dynamic metapopulation in the face of high environmental perturbations. Implications Increased juvenile mortality above current levels – for example through the spread of cane toads or invasion of feral cats – may have serious implications for the persistence of the current network of northern quoll populations and other mammals that exhibit population fragmentation in arid environments. Estimates of survival rates for the juvenile cohort of quolls would improve diagnosis of a species’ population dynamics as well as inform practitioners of key life-history sensitivities.

Abstract ContextAustralia has experienced the highest number of mammal extinctions of any continent over the past two centuries. Understanding the demography and spatial requirements of populations before declines occur is fundamental to confirm species trajectory, elucidate causes of decline and develop effective management strategies. AimsWe evaluated the demography and spatial requirements of a northern quoll, Dasyurus hallucatus, population on Groote Eylandt, Northern Territory. Groote Eylandt is considered a refuge for the species because key threatening processes are absent or limited; cane toads and introduced ungulates are absent, feral cats are infrequently detected and the fire regime is benign compared with mainland Northern Territory. MethodsWe conducted a 4-year capture–mark–recapture study to monitor growth, reproduction and survival of northern quolls within a 128-ha area, and we evaluated spatial requirements by attaching GPS units to both sexes. To assess the status of the Groote Eylandt population, we compared the demographics with existing data from mainland populations. Key resultsThe average density of northern quolls was 0.33ha−1. However, there was a 58% decline in female density, primarily between 2012 and 2013, corresponding with a decrease in female body mass. Females survived and bred in up to 3 years and adult survival rates did not vary among years, suggesting that juvenile recruitment drives population fluctuations. Male quolls were semelparous, with die-off occurring in the months following breeding. The median female and male home ranges were 15.7ha and 128.6ha respectively, and male ranges increased significantly during breeding, with 1616ha being the largest recorded. ConclusionsThe northern quoll population on Groote Eylandt had a higher density, female survival and reproductive success than has been previously recorded on the mainland. However, a marked decline was recorded corresponding with a decrease in female mass, indicating below-average rainfall as the likely cause. ImplicationsGroote Eylandt remains a refuge for the endangered northern quoll. However, even in the absence of key threatening processes, the population has declined markedly, highlighting the impact of environmental fluctuations. Maintaining the ecological integrity of Groote Eylandt is imperative for population recovery, and managing threats on the mainland over appropriate spatial scales is necessary to increase population resilience.

Development and growth of Planigale tenuirostris are described with data for three litters bred in the laboratory. Growth curves were constructed for the length of head plus body, tail, head and foot; the width of head and scrotum and the body weight for the period from birth to 200 days old. A regression equation is given that predicts age during the first 30 days of life. The young of P. tenuirostris first detached from the teats at 36 days, had their eyes open at 51 days and were weaned at 95 days. Field data on development are in agreement with those for the laboratory individuals. Features of development, growth and maternal nesting behaviour are compared with those known for other small dasyurids.

We know little about the availability of potential prey and patterns of prey consumption by Ningaui yvonneae in a natural environment. This information is important to understanding how the species is able to exploit its semiarid environment. Here, we examine the diet of N. yvonneae inhabiting a semiarid mallee community in South Australia using a combination of faecal analysis and observations of nocturnally foraging animals. Prey consumption was compared with the availability of prey types in the environment, and comparisons made between habitat components, across seasons and between sexes. N. yvonneae was found to include a range of prey types in its diet, with 11 invertebrate taxa recorded from direct observation and eight of these detected in the scats. Prey taxa consumed most often by freely foraging ningauis were Araneae, Blattodea and Orthoptera, while those most commonly detected in scats were Hymenoptera and Araneae. In comparison, 22 invertebrate taxa were recorded in pitfall traps, although many of these were recorded infrequently. Taxa most commonly recorded in traps were Hymenoptera, Collembola, Coleoptera and Acariformes. Observational data also indicated that consumption of prey taxa differed significantly between sexes and among seasons. Males generally consumed a more diverse array of prey, with both observational and scat data showing that they were more likely to consume Hymenoptera and Isoptera, while females were more likely to consume Lepidoptera and Hemiptera. Variability between seasons was evident in consumption of invertebrate grubs (recorded only during ‘growth’; February–April), Orthoptera (recorded most often during ‘breeding’, August–October), and Araneae (recorded more often during ‘maturation’, May–July). However percentage occurrence data from the scats lacked this seasonality, possibly because of the smaller array of prey taxa recorded. N. yvonneae captured prey from all available habitat components, with five of the most frequently recorded prey taxa being recorded from all components. Leaf litter and Triodia were the most commonly recorded capture sites (45% and 22% of captures respectively), and males and females used the habitat components in a similar manner. Although N. yvonneae is like many other dasyurids in having a largely generalist insectivorous diet, comparisons of prey consumed with their availability in the environment indicated that individuals did show some selectivity towards certain taxa, particularly Blattodea, Orthoptera, Chilopoda, Lepidoptera and Araneae.

Sexual dimorphism in animals has been recognised as being associated with particular breeding strategies or mating systems since Darwin's Origin of Species. Frequently, in polygamous situations, females express a variety of attributes to attract males, and males compete with each other for access to females. This produces different selective pressures in each sex, which in tum produces differing morphologies (Leigh 1995). Thus, the emphasis of morphological studies of sexual differences tends to focus on adults and not the growth patterns that generate those differences. Growth patterns in marsupials have been shown to be variable between species (Gemmell and Hendrikz 1993). Previous studies of dasyurid species in captivity concluded that the onset of dimorphism occurs prior to or during weaning (Whitford, Fanning and White 1982; Williams and Williams 1982), but wild animals are not sexually dimorphic until after weaning (Soderquist 1995). These studies have generally examined the growth rates of males and females and the timing of the onset of sexual dimorphism, but little attention has been focussed on how the differences between the sexes are generated.

Interest in the conservation and welfare of Australian native wildlife continues to grow. Veterinarians are frequently presented with injured, diseased or orphaned animals and there is increasing veterinary involvement in conservation programs. In Australia and overseas, Australian mammals are used in research, kept as pets and are popular display and education animals in zoos and fauna parks. The recognition, diagnosis and treatment of injury and disease in wildlife species present unique challenges for the veterinarian. Radiology is a fundamental diagnostic tool that can be used to further define the nature and extent of injury or disease, guide therapeutic decisions and determine prognosis. An essential aspect of radiology is the recognition and description of abnormal findings. In order to recognise abnormalities, knowledge of normal radioanatomy is necessary. Radiology of Australian Mammals provides a detailed reference on the normal radioanatomy of Australian mammals. A chapter on radiographic technique covers digital radiography of small species, and restraint and positioning to obtain diagnostic images. This is followed by chapters covering the normal radioanatomy of the short-beaked echidna, platypus, macropods, koala, wombats, dasyurids, possums and gliders, bandicoots and the bilby, and bats. Each chapter includes a detailed description of anatomy relevant to radiography and multiple images of normal radiographs with outlines and annotations identifying relevant structures. A chapter on dental radiology discusses and demonstrates normal dental radioanatomy. The final chapter includes selected radiographic pathology case studies providing an appreciation of radiographic findings seen in some common diseases of Australian mammals. A checklist of the mammals of Australia and its territories and a glossary of abbreviations and terms used for annotation of images complete the volume.