Scent detection dogs as a novel method for oestrus detection in an endangered species, the Tasmanian devil (Sarcophilus harrisii)

Captive breeding is a critical tool for conservation of endangered species. Identifying the correct time to pair males and females can be a major challenge for captive breeding programmes, with current methods often being invasive or slow. Detection dogs may provide a non-invasive way to determine female receptivity, but this has not been explored in captive wildlife. This exploratory study investigated the use of detection dogs as a novel method of oestrus detection in the endangered Tasmanian devil (Sarcophilus harrisii). Faecal samples were collected from 11 captive female devils during the breeding seasons of 2020 and 2021. Three dogs with prior detection experience were trained and subsequently assessed (n = 188 searches per dog), on their ability to discriminate between oestrus and non-oestrus devil faecal samples, in a one sample set-up. When assessed on training samples, dogs were able to correctly discriminate oestrus from non-oestrus with a mean sensitivity of 69.1% and mean specificity of 65.7%. When assessed on novel samples, their sensitivity to oestrus dropped (mean sensitivity of 48.6%). However, they were still able to correctly identify non-oestrus samples (mean specificity of 68.1%). This study is the first to explore detection dogs' ability to identify oestrus in a captive breeding programme for endangered wildlife, providing a promising tool for non-invasive monitoring of reproductive status in wildlife.

Application of Reproductive Technologies to the Critically Endangered Baw Baw Frog, Philoria frosti

Reproductive technologies (RTs) can assist integrated conservation breeding programs to attain propagation targets and manage genetic diversity more effectively. While the application of RTs to enhance the conservation management of threatened amphibians has lagged behind that of other taxonomic groups, a recent surge in research is narrowing the divide. The present study reports on the first application of RTs (hormone-induced spawning, hormone-induced sperm-release, and sperm cryopreservation) to the critically endangered Baw Baw frog, Philoria frosti. To determine the effect of hormone therapy on spawning success, male-female pairs were administered either 0 μg/g gonadotropin-releasing hormone agonist (GnRHa), 0.5 μg/g GnRHa, or 0.5 μg/g GnRHa + 10 μg/g metoclopramide (MET) (n = 6-7 pairs/treatment), and the number of pairs ovipositing, total eggs, and percent fertilisation success were quantified. To determine the effect of hormone therapy on sperm-release and to establish the peak time to collect sperm post-hormone administration, males were administered 0 IU/g (n = 4), or 20 IU/g hCG (n = 16). Total sperm, sperm concentration, and percent viability were quantified at 0, 2, 4, 6, 8, 10, and 12 h post-hormone administration. Overall, the percentage of pairs ovipositing was highest in the GnRHa + MET treatment, with 71% of pairs ovipositing, compared to 57% and 33% of pairs in the GnRHa and control treatments, respectively. The quantity of sperm released from males in response to hCG peaked at 4 h post-hormone administration, though it remained high up to 12 h. The percent sperm viability also peaked at 4 h post-administration (94.5%), exhibiting a steady decline thereafter, though viability remained above 77% throughout the 12 h collection period. The remaining sperm samples (n = 22) were cryopreserved using established protocols and biobanked for long-term storage and future conservation applications. The mean post-thaw sperm viability was 59%, and the percent total motility was 17%. The results from this preliminary study will direct further applications of RTs to the critically endangered Baw Baw frog to assist with species recovery.

The plastic pandemic: COVID-19 has accelerated plastic pollution, but there is a cure

Plastic pollution is now present in all areas of our planet, including its last wilderness, Antarctica, and the plastic crisis has further escalated because of COVID-19. The pandemic has caused a significant increase in the global consumption of single-use protective items such as masks and gloves. These and other plastic items add to the suite of plastic pollution issues, from entanglement of wildlife to microplastic bioaccumulation. Given plastics are a major threat facing humans and wildlife, swift action to reduce plastic pollution is urgently needed. Solutions to plastic pollution are within reach. With collective, impactful action we will ensure a better future for our planet and ourselves. Here, we propose several measures for decision-makers to implement to achieve a solution and tackle plastic pollution as a united, global community.

Sniffing out danger: rapid antipredator training of an endangered marsupial

Globally, predator aversion training has assisted naive prey species to learn to evade introduced predators, improving translocation success. Eastern barred bandicoots (Perameles gunnii; hereafter ‘bandicoot’) are extinct on mainland Australia due to habitat loss and introduced predators, and are the focus of a long-term captive breeding and reintroduction program. Our trials showed that captive bandicoots failed to recognise cat (Felis catus) scents as belonging to a predator, suggesting prey naivety towards cats. We trialled five stimuli to elicit short-term fear behaviour in bandicoots. An automatic compressed air spray and automatic bin lid were most effective. We coupled these stimuli with cat urine during predator aversion training and presented them to bandicoots on three occasions. Bandicoots learnt to avoid the area containing cat urine, suggesting bandicoots are capable of learning new behaviours rapidly. Six trained and five untrained captive bandicoots where released onto Summerland Peninsular, Phillip Island (with cat densities at 1.1 cats/km2). Both had high survival and recapture rates 7 months after release. Training endangered species to avoid introduced predators could assist with long-term species recovery.

Torn limb from limb: the ethology of prey-processing in Tasmanian devils (Sarcophilus harrisii)

The success of carnivorous mammals is determined not only by their ability to locate and kill prey, but also their efficiency at consuming it. Breaking large prey into small pieces is challenging due to the strong and tough materials that make up a carcass (e.g. hide, muscle, and bone). Carnivores therefore require a diverse suite of prey-processing behaviours to utilise their catch. Tasmanian devils are Australia’s only large marsupial scavengers and have the ability to consume almost all of a carcass. To determine how they do this we analysed 5.5 hours of footage from 21 captive and wild devils feeding at carcasses. We documented 6320 bouts of 12 distinct prey-processing behaviours, performed at frequencies that varied throughout feeds and between groups. The time point in the feed influenced the types of behaviours used. This is likely due to changing prey size, as different techniques appear better suited to handling whole carcasses or large pieces (pulling and pinning) or smaller pieces (holding and manipulating). Group size impacted the frequency of social pulling behaviours, which increased with the number of animals. Our findings highlight the range of prey-processing behaviours performed by scavenging devils when handling, breaking down, and consuming a carcass. The devils’ repertoire shares similarities with large carnivores that handle and consume whole carcasses as well as small carnivores that are adept in grasping and handling smaller prey.

Wearing the devil down: Rate of tooth wear varies between wild and captive Tasmanian devils

Mammalian carnivores rely on their sharp teeth to effectively kill and consume prey. However, over time this causes wear and breakage that alters tooth shape, reducing their effectiveness. Extreme tooth wear and damage is especially prevalent in species that scavenge carcasses, like the Tasmanian devil (Sarcophilus harrisii), which are well known for their voracious appetites and ability to consume almost all of a carcass, including bone. In this study, we comprehensively describe tooth wear in captive and wild devils to look for differences in the patterns and rate of wear between these environments. To do this we surveyed tooth condition in skulls from 182 wild and 114 captive devils for which age was estimated using canine over-eruption. We found the types of tooth wear documented were the same in captive and wild devils, but captive animals have less severe wear than wild devils of the same estimated age. There was no difference in the proportion of captive or wild individuals with broken canine or molar teeth; however, breakage occurred at a younger age in wild devils. Although not considered anomalous or harmful, this indicates a difference in the way teeth are being used and/or the foods consumed between captive and wild devils. We hypothesize how these results relate to differences in diet or behavior that may stem from their various feeding environments, for example, higher quality food (fresh, whole, and yet to be scavenged carcasses) provided to captive devils likely causes less wear. Further, we support management options that closely replicate wild diet items and behaviors suitable for a long-term insurance population.

Eat your heart out: choice and handling of novel toxic prey by predatory water rats

We investigated predator–prey interactions between cane toads (Rhinella marina) and native water rats (Hydromys chrysogaster), where toads are novel prey. We show that wild water rats preferentially targeted larger toads, and consumed specific non-toxic organs only. Rats either rapidly learned these behaviours, or adapted them from hunting native frogs.

Maternal care of platypus nestlings (Ornithorhynchus anatinus)

Maternal care in platypuses has never been rigorously studied due to the difficulty in locating and accessing nesting burrows. Here we describe the maternal behaviour of a captive female platypus and the growth and development of her offspring over 11 breeding seasons. We located a nesting burrow and inserted a camera to record the activity and behaviour of the female and her offspring. We also measured the female’s food intake during lactation. The ages of the offspring were assigned to developmental milestones including opening of the eyes and development of pelage. Twins (n=4) were left alone for periods longer than 24h by the mother at an earlier age than single nestlings (n=2). The dietary energy intake of the breeding female was more than double that of non-lactating females in the last month of lactation, indicating the large energy requirements of milk production. The mean age of young at emergence from the burrow was 128±1 days and in 60% of nestlings emergence occurred after weaning. This suggests a rapid transition from a completely milk-based diet to a diet of aquatic macroinvertebrates. The techniques we developed have allowed us to study maternal care in platypuses and the development of nestlings, both of which were previously only poorly understood.

Burrow use by juvenile platypuses (Ornithorhynchus anatinus) in their natal home range

We determined patterns of burrow use by juvenile platypuses (Ornithorhynchus anatinus) in their natal home range, and evaluated associations between burrows and vegetation. Between March 2015 and March 2017, we captured seven juvenile platypuses along a 3-km stretch of Badger Creek, Victoria and fitted them with radiotransmitters. We recorded the locations of animals in their burrows daily while transmitters were attached (range: 14–132 days). Juveniles used 74 different burrows, with each using 11 ± 2 burrows. Overall, 65% of burrows (48) were used once, 22% (16) were used between 2 and 9 times (moderate-use), and 13% (10) were used frequently (> 10 times). No juveniles dispersed during the monitoring period (14–132 days). Although some association was observed between burrow use and particular vegetation communities, vegetation was not a strong factor driving site selection of burrows. Use of multiple burrows may allow juveniles to avoid competition with conspecifics, reduce exposure to ectoparasites, and develop shelter-seeking behavior. Juvenile platypuses remained in their natal home range, where conditions are likely to be good because they supported recent breeding, while completing their growth and development prior to dispersal.

Identification of threatened rodent species using infrared and white-flash camera traps

Camera trapping has evolved into an efficient technique for gathering presence/absence data for many species; however, smaller mammals such as rodents are often difficult to identify in images. Identification is inhibited by co-occurrence with similar-sized small mammal species and by camera set-ups that do not provide adequate image quality. Here we describe survey procedures for identification of two small, threatened rodent species – smoky mouse (Pseudomys fumeus) and New Holland mouse (P. novaehollandiae) – using white-flash and infrared camera traps. We tested whether observers could accurately identify each species and whether experience with small mammals influenced accuracy. Pseudomys fumeus was ~20 times less likely to be misidentified on white-flash images than infrared, and observer experience affected accuracy only for infrared images, where it accounted for all observer variance. Misidentifications of P. novaehollandiae were more common across both flash types: false positives (>0.21) were more common than false negatives (<0.09), and experience accounted for only 31% of variance in observer accuracy. For this species, accurate identification appears to be, in part, an innate skill. Nonetheless, using an appropriate setup, camera trapping clearly has potential to provide broad-scale occurrence data for these and other small mammal species.

Female control of reproductive behaviour in the platypus (Ornithorhynchus anatinus), with notes on female competition for mating

Opportunities for studying platypus courtship and mating behaviours in the wild are limited due to the nocturnal and cryptic nature of this species. We report on platypus courtship and mating behaviour from a successful breeding program at Healesville Sanctuary, Victoria, in which platypuses were held as either breeding pairs or trios over seven years. Behaviour was recorded daily on infrared cameras resulting in over 80,000 h of footage that was analysed for activity periods, and courtship and mating behaviours including non-contact and contact courtship, mating and avoidance. Our aims were to describe and quantify courtship and mating interactions between males and females, and to determine if either sex controlled the initiation and continuation of the behaviours. From our observations, we describe a new courtship behaviour, non-contact courtship, which constituted the majority of all mating season interactions between males and females. The time between first and last appearance of a courtship and mating behaviour was 41.0 ± 6.6 days, with the females showing behavioural receptivity for 29.6 ± 5.1 days. Female platypuses used three evasive strategies in relation to approaches by males: avoidance, flight and resistance. Females controlled the duration of 79% of encounters using resistance. For the first time, two females were seen competing with each other over access to the male platypus in their enclosure and for nesting material. Time investment in courtship and mating behaviours was a poor indicator of receptivity and breeding success, and we suggest that breeding failure is more likely to be associated with failure of fertilisation, nest building, embryonic development or incubation. We describe how female platypuses demonstrate evasiveness and control of courtship and mating behaviours, and the importance of providing these opportunities in captivity to promote successful breeding.

One size does not fit all: Monitoring faecal glucocorticoid metabolites in marsupials

Marsupial research, conservation, and management can benefit greatly from knowledge about glucocorticoid (GC) secretion patterns because GCs influence numerous aspects of physiology and play a crucial role in regulating an animal's response to stressors. Faecal glucocorticoid metabolites (FGM) offer a non-invasive tool for tracking changes in GCs over time. To date, there are relatively few validated assays for marsupials compared with other taxa, and those that have been published generally test only one assay. However, different assays can yield very different signals of adrenal activity. The goal of this study was to compare the performance of five different enzyme immunoassays (EIAs) for monitoring adrenocortical activity via FGM in 13 marsupial species. We monitored FGM response to two types of events: biological stressors (e.g., transport, novel environment) and pharmacological stimulation (ACTH injection). For each individual animal and assay, FGM peaks were identified using the iterative baseline approach. Performance of the EIAs for each species was evaluated by determining (1) the percent of individuals with a detectable peak 0.125-4.5days post-event, and (2) the biological sensitivity of the assay as measured by strength of the post-event response relative to baseline variability (Z-score). Assays were defined as successful if they detected a peak in at least 50% of the individuals and the mean species response had a Z⩾2. By this criterion, at least one assay was successful in 10 of the 13 species, but the best-performing assay varied among species, even those species that were closely related. Furthermore, the ability to confidently assess assay performance was influenced by the experimental protocols used. We discuss the implications of our findings for biological validation studies.

Seasonal changes in food selection and nutrition of captive platypuses (Ornithorhynchus anatinus)

Anecdotal observations of captive platypuses (Ornithorhynchus anatinus) suggest that they show a seasonal preference for particular foods, but this has never been rigorously measured. This study aimed to determine seasonal food preferences and energy consumption of captive platypuses so that better protocols for maintaining platypuses in captivity can be developed. Seven platypuses were fed an ad libitum diet with all food items weighed in and out of tanks. Food items were analysed for energy, fats, carbohydrates, proteins, vitamins and minerals. Platypuses preferred less mobile prey (mealworms, earthworms and fly pupae) over highly mobile prey (crayfish). There was no significant seasonal change in preference for different dietary items, which is more likely to be driven by prey behaviour. Crayfish contributed the largest percentage (mass) consumed and was highly nutritious. While the relative percentage of items in the diet did not change seasonally, the quantity eaten did. The mean energy intake of platypuses was 921 kJ kg–1 day–1 and varied seasonally, being lowest during the breeding season (810 kJ kg–1 day–1) and highest in the postbreeding season (1007 kJ kg–1 day–1). These changes were associated with preparation and recovery from the breeding season. We conclude that the platypus diet is influenced by nutrition and seasonal factors as well as by prey behaviour. This knowledge will contribute to improving the husbandry and management of platypuses, which are widely recognised as difficult to maintain in captivity.

The value of eutherian-marsupial comparisons for understanding the function of glucocorticoids in female mammal reproduction

This article is part of a Special Issue "SBN 2014". Chronic stress is known to inhibit female reproductive function. Consequently, it is often assumed that glucocorticoid (GC) concentrations should be negatively correlated with reproductive success because of the role they play in stress physiology. In contrast, a growing body of evidence indicates that GCs play an active role in promoting reproductive function. It is precisely because GCs are so integral to the entire process that disruptions to adrenal activity have negative consequences for reproduction. The goal of this paper is to draw attention to the increasing evidence showing that increases in adrenal activity are important for healthy female reproduction. Furthermore, we outline several hypotheses about the functional role(s) that GCs may play in mediating reproduction and argue that comparative studies between eutherian and marsupial mammals, which exhibit some pronounced differences in reproductive physiology, may be particularly useful for testing different hypotheses about the functional role of GCs in reproduction. Much of our current thinking about GCs and reproduction comes from research involving stress-induced levels of GCs and has led to broad assumptions about the effects of GCs on reproduction. Unfortunately, this has left a gaping hole in our knowledge about basal GC levels and how they may influence reproductive function, thereby preventing a broader understanding of adrenal physiology and obscuring potential solutions for reproductive dysfunction.

Assortative mating among animals of captive and wild origin following experimental conservation releases

Captive breeding is a high profile management tool used for conserving threatened species. However, the inevitable consequence of generations in captivity is broad scale and often-rapid phenotypic divergence between captive and wild individuals, through environmental differences and genetic processes. Although poorly understood, mate choice preference is one of the changes that may occur in captivity that could have important implications for the reintroduction success of captive-bred animals. We bred wild-caught house mice for three generations to examine mating patterns and reproductive outcomes when these animals were simultaneously released into multiple outdoor enclosures with wild conspecifics. At release, there were significant differences in phenotypic (e.g. body mass) and genetic measures (e.g. Gst and F) between captive-bred and wild adult mice. Furthermore, 83% of offspring produced post-release were of same source parentage, inferring pronounced assortative mating. Our findings suggest that captive breeding may affect mating preferences, with potentially adverse implications for the success of threatened species reintroduction programmes.

Females Choose Mates Based on Genetic Relatedness in a Small Dasyurid Marsupial, the Agile Antechinus (Antechinus agilis)

Females in a variety of taxa mate with more than one male during a single oestrus and exhibit mate preferences for genetically compatible males, but the influence of female mate choice on siring success is not clearly understood. Whether females choose to mate with more than one male or endure forced copulations is also often unknown. Here, we examined the effects of genetic relatedness on female mate choice and siring success in a small semelparous carnivorous marsupial, the agile antechinus (Antechinus agilis), during two consecutive breeding seasons. Experimental trials were conducted in captivity over periods of 72 hours using interconnected enclosures in which female antechinus could choose to access any of four separated males, but males were only able to access females that entered their quarters. Females had access to two genetically similar and two genetically dissimilar males simultaneously and all behavioural interactions were observed and scored from continuous video recordings. Genetic similarity between mates and paternity of young was determined by microsatellite analyses. Some females chose to enter and mate with more than one male during a single oestrus period. Although females investigated all males, they spent significantly more time visiting, and mated more times with, genetically dissimilar males. Males that were genetically dissimilar to the female sired 88% of subsequent offspring. Whilst males mated readily with most females, they rejected the advances of some receptive females, indicating a previously unexpected level of male mate choice. The results show that genetic relatedness between mates has a significant influence on mate choice, breeding and siring success in the agile antechinus.

Effects of drought on weight, survival and breeding success of agile antechinus (Antechinus agilis), dusky antechinus (A. swainsonii) and bush rats (Rattus fuscipes)

Extreme weather conditions, such as drought, significantly decrease the survival and breeding success of numerous species. Despite the frequent occurrence of such conditions in Australia, little is known about the effects of changing environmental conditions on the native small mammals. This study, conducted from 2002 to 2004, focussed on sympatric wild populations of the agile antechinus (Antechinus agilis), with more limited information on the dusky antechinus (A. swainsonii) and the bush rat (Rattus fuscipes). Bodyweights of agile antechinus before and during the breeding season were significantly lower in 2003 (drought) than in 2002 or 2004. Survival of female agile antechinus and the number of young per litter also decreased significantly during drought. In contrast, the dusky antechinus showed no difference in mean bodyweights between years, high survival rates of females and similar litter sizes in 2002 and 2003. There was also no difference in bodyweight of bush rats between years. Low rainfall was recorded during pregnancy and lactation in the agile antechinus, but rainfall was higher during pregnancy and lactation in the dusky antechinus. The survival and breeding success of the agile antechinus may have been adversely affected by a combination of interspecific competition, timing of the breeding season and severity of the drought.

Genetic similarity, not male size, influences female mate choice in the agile antechinus (Antechinus agilis)

Our research investigates the effects of genetic relatedness between mates and male size on female mate choice in the agile antechinus (Antechinus agilis). Females were provided with a simultaneous choice between one large and one small male, with a minimum 5 g (~20% of male weight) difference between males, in specially designed mate-choice enclosures. Genetic relatedness between males and females was determined using highly polymorphic, species-specific, microsatellite markers. Male size did not influence mate choice, with approximately equal numbers of large and small males chosen. Females chose males that were more genetically dissimilar to themselves significantly more times and showed significantly more sexual and non-exploratory behaviours near the genetically dissimilar males. The results show that, when free female mate choice is possible, female agile antechinus choose males on the basis of genetic relatedness, rather than male size.

Multiple paternity and communal maternal care in the feathertail glider (Acrobates pygmaeus)

It has been predicted, on the basis of morphological and behavioural evidence, that female feathertail gliders (Acrobates pygmaeus) will mate with multiple males within a single oestrus and that multiple paternity may occur in their litters. To determine whether feathertail glider litters are sired by multiple males, DNA collected from 10 litters and their mothers was tested for hereditary polymorphisms. The techniques used to evaluate paternity included AFLP (amplified fragment length polymorphisms), RAPD (randomly amplified polymorphic DNA) and RAMP (randomly amplified microsatellite polymorphisms) analyses and microsatellite markers. Although most genetic techniques produced only monomorphic bands, analyses with AFLPs indicated that multiple paternity did occur in six of eight litters, confirming that multiple mating within a single oestrous period occurs in this species. Results further indicated that mothers care for young other than their own. On the basis of their high testes-to-bodyweight ratio, male-biased sexual size dimorphism and multiple paternity in litters, sperm competition is considered highly likely to occur in this species.