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The duck‐billed platypus (Ornithorhynchus anatinus) is currently listed as near‐threatened. A key part of the conservation strategy for this species is its captive maintenance; however, captive animals often have dysbiotic gut bacterial microbiomes. Here, for the first time, we characterize the gut microbiome of wild platypus via fecal samples using high‐throughput sequencing of the bacterial 16S rRNA gene and identify microbial biomarkers of captivity in this species. At the phylum level, Firmicutes (50.4%) predominated among all platypuses, followed by Proteobacteria (28.7%), Fusobacteria (13.4%), and Bacteroidota (6.9%), with 21 "core" bacteria identified. Captive individuals did not differ in their microbial α‐diversity compared to wild platypus but had significantly different community composition (β‐diversity) and exhibited higher abundances of Enterococcus, which are potential pathogenic bacteria. Four taxa were identified as biomarkers of wild platypus, including Rickettsiella, Epulopiscium, Clostridium, and Cetobacterium. This contrast in gut microbiome composition between wild and captive platypus is an essential insight for guiding conservation management, as the rewilding of captive animal microbiomes is a new and emerging tool to improve captive animal health, maximize captive breeding efforts, and give reintroduced or translocated animals the best chance of survival. [ABSTRACT FROM AUTHOR]

Summary Platypus (Ornithorhynchus anatinus) are an endemic Australian freshwater mammal, impacted by synergistic threats across their range. During the extreme drought of 2017–2019, declining water levels threatened Platypus at Tidbinbilla Nature Reserve (TNR), Australian Capital Territory (ACT), Australia. TNR supports a population of Platypus, occupying interconnected ponds within a predator proof fence. During drought conditions in 2019, Platypuses could not move out of the fenced area to refugia as floodgates were closed due to low water levels. In winter of 2019, eight Platypuses were found deceased resulting from starvation. By December, water levels were extremely low and ponds were continuing to dry. Given these circumstances, a rescue intervention was undertaken to capture stranded Platypuses. They were temporarily relocated and housed at Taronga Zoo, Sydney, until they were returned when conditions at TNR improved. Seven Platypuses were rescued, with five successfully housed at Taronga for 5 months. One Platypus was lost after escaping from its enclosure and another Platypus died when trapped in a crevice. The Platypuses were returned after water levels increased at TNR and were monitored for 500 days post‐release, demonstrating successful repatriation. This case study outlines the key stages and considerations required for this intervention, providing critical information for rescue attempts on drought‐affected Platypus populations. There is a need to continue developing a decision framework for interventions of climate‐affected populations, including quantifying trigger thresholds and conservation prioritisation of populations. This will become increasingly necessary given the trajectories of habitat degradation, coupled with the increasingly frequent and severe droughts, expected under anticipated climate change scenarios. [ABSTRACT FROM AUTHOR]

Although monotremes diverged from the therian mammal lineage approximately 187 million years ago, they retain various plesiomorphic and/or reptilian‐like anatomical and physiological characteristics. This study examined the morphology of juvenile and adult female reproductive tracts across various stages of the presumptive oestrous cycle, collected opportunistically from cadaver specimens submitted to wildlife hospitals during the breeding season. In adult females, ovaries had a convoluted cortex with follicles protruding from the ovarian surface. While protruding antral follicles were absent from the ovaries of juvenile echidnas, histological analysis identified early developing primordial and primary follicles embedded into the ovarian cortex. The infundibulum epithelial cells of the oviducts were secretory during the follicular phase but not at other stages, the ampulla region was secretory at all stages and is likely responsible for the mucoid layer deposited around the zona pellucida, and the isthmus region of the oviduct appeared to be responsible for initial deposition of the shell coat, as in marsupials. Female echidnas have two separate uteri, which never merge and enter separately into the urogenital sinus (UGS). This study confirmed that both uteri are functional and increase in glandular activity during the luteal phase. In the juvenile uteri, the endometrium was immature with minimal, small uterine glands. A muscular cervical region at the caudal extremity of each uterus, just before the cranial region of the UGS was defined by the absence of glandular tissue in all female echidnas, including the juveniles. There was no evidence of a definitive vaginal region. A clitoris was also detected that possessed a less developed but similar structural (homologous) anatomy to the male penis; urethral ducts while present did not appear to be patent. [ABSTRACT FROM AUTHOR]

It is possible that the reproductive strategy of the short-beaked echidna is related to seasonal changes in fat deposition and energy availability, regulated by seasonal changes in endocrine function. We predicted that circulating leptin levels would be directly proportional to adiposity during most of the year, but that a change in this relationship would occur during the pre-breeding season to allow increased fat deposition. To test this hypothesis, we made use of a captive colony of echidnas to describe and quantify changes in fat distribution and the adipostatic hormone leptin. First we assessed seasonal changes in circulating leptin levels, body mass and adiposity for three male and three female adult echidnas maintained on a standard diet. Second, we explored the relationship between circulating leptin levels and increased caloric intake for an additional five adult female echidnas that were provided with supplemented nutrition. Third we visualised fat distribution in male and female adult echidnas using magnetic resonance imaging (MRI) before and after the breeding season, to determine where fat is deposited in this species. For echidnas maintained on the standard diet, there were no seasonal changes in body mass, body fat or plasma leptin levels. However, female echidnas provided with supplemented nutrition had significantly elevated plasma leptin levels during the breeding season, compared to the pre-and post- breeding periods. MRI showed substantial subcutaneous fat depots extending dorso-laterally from the base of the skull to the base of the tail, in both sexes. Pre-breeding season, both sexes had considerable fat deposition in the pelvic/rump region, whilst the female echidna accumulated most fat in the abdominal region. This study shows that male and female echidnas accumulate body fat in the pelvic/rump and the abdominal regions, respectively and that circulating leptin may promote fattening in female echidnas during the breeding season by means of leptin resistance. However, further research is required to evaluate the precise relationship between seasonal changes in leptin and adiposity. [ABSTRACT FROM AUTHOR]

Context: River regulation affect freshwater species by disrupting the natural flow regime and connectivity. Aims: Investigate the impact of river regulation on platypus populations on four regulated rivers within the northern Murray–Darling Basin. Methods: Assessment of hydrology, live trapping downstream of large dams, multi-species environmental DNA surveys in upstream and downstream sections. Key results: There were significant changes in flow seasonality and cold-water pollution as a result of river regulation. Upstream sections experienced prolonged periods of ceased flow, most recently during an extreme drought between 2017 and 2020. eDNA surveys detected platypuses downstream of all dams but failed to find evidence of them upstream in two rivers, indicating possible local extinctions. Capture of four platypuses in the Severn River and four, in very poor condition, in the Peel River, and none in the Gwydir River or Pike Creek–Dumaresq River. Significant differences in macroinvertebrate communities, implying possible impacts on platypus diet. Conclusions: River regulation and habitat fragmentation affect platypus populations, namely disappearance from upstream sections, low downstream capture rates and the poor body condition. Implications: Urgent need for catchment-scale river management strategies that preserve ecological functions and connectivity and improve resilience to protect and sustain platypus populations, indicating directions for future research and conservation efforts. This study has shown how river regulation in the northern Murray–Darling Basin affects platypus populations, altering their habitats and food sources. Through trapping and DNA analysis, researchers found platypuses struggling downstream of dams, with potential local extinctions upstream, possibly with no access to drought refugia. The findings call for improved river management to safeguard these unique creatures and their ecosystems. This article belongs to the collection Environmental Flows in Northern Murray–Darling Basin: what we know about the science and management after a decade of practice. [ABSTRACT FROM AUTHOR]

We report on a male platypus (Ornithorhynchus anatinus) who was tagged in November 2000 at the age of 1 year and recaptured in September 2023, when nearly 24 years old, in a small creek system in Melbourne's southeastern suburbs. By comparison, a female platypus recently reached the age of 30 years in captivity, though with signs of ageing that may have precluded her survival if she were living in the wild. Ten other captive individuals have lived to an age of more than 20 years in recent decades. A new platypus longevity record in the wild (nearly 24 years) has been confirmed for a male living in a creek in Melbourne's southeastern suburbs. In captivity, a female platypus recently reached the age of 30 years at Healesville Sanctuary. Photograph by Barry Baker. [ABSTRACT FROM AUTHOR]

Abstract Egg-laying mammals (monotremes) are considered “primitive” due to traits such as oviparity, cloaca, and incomplete homeothermy, all of which they share with reptiles. Two groups of monotremes, the terrestrial echidna (Tachyglossidae) and semiaquatic platypus (Ornithorhynchidae), have evolved highly divergent characters since their emergence in the Cenozoic era. These evolutionary differences, notably including distinct electrosensory and chemosensory systems, result from adaptations to species-specific habitat conditions. To date, very few studies have examined the visual adaptation of echidna and platypus. In the present study, we show that echidna and platypus have different light absorption spectra in their dichromatic visual sensory systems at the molecular level. We analyzed absorption spectra of monotreme color opsins, long-wavelength sensitive opsin (LWS) and short-wavelength sensitive opsin 2 (SWS2). The wavelength of maximum absorbance (λ max) in LWS was 570.2 in short-beaked echidna (Tachyglossus aculeatus) and 560.6 nm in platypus (Ornithorhynchus anatinus); in SWS2, λ max was 451.7 and 442.6 nm, respectively. Thus, the spectral range in echidna color vision is ~ 10 nm longer overall than in platypus. Natural selection analysis showed that the molecular evolution of monotreme color opsins is generally functionally conserved, suggesting that these taxa rely on species-specific color vision. In order to understand the usage of color vision in monotremes, we made 24-h behavioral observations of captive echidnas at warm temperatures and analyzed the resultant ethograms. Echidnas showed cathemeral activity and various behavioral repertoires such as feeding, traveling, digging, and self-grooming without light/dark environment selectivity. Halting (careful) behavior is more frequent in dark conditions, which suggests that echidnas may be more dependent on vision during the day and olfaction at night. Color vision functions have contributed to dynamic adaptations and dramatic ecological changes during the ~ 60 million years of divergent monotreme evolution. The ethogram of various day and night behaviors in captive echidnas also contributes information relevant to habitat conservation and animal welfare in this iconic species, which is locally endangered.

Egg-laying mammals (monotremes) are considered "primitive" due to traits such as oviparity, cloaca, and incomplete homeothermy, all of which they share with reptiles. Two groups of monotremes, the terrestrial echidna (Tachyglossidae) and semiaquatic platypus (Ornithorhynchidae), have evolved highly divergent characters since their emergence in the Cenozoic era. These evolutionary differences, notably including distinct electrosensory and chemosensory systems, result from adaptations to species-specific habitat conditions. To date, very few studies have examined the visual adaptation of echidna and platypus. In the present study, we show that echidna and platypus have different light absorption spectra in their dichromatic visual sensory systems at the molecular level. We analyzed absorption spectra of monotreme color opsins, long-wavelength sensitive opsin (LWS) and short-wavelength sensitive opsin 2 (SWS2). The wavelength of maximum absorbance (λmax) in LWS was 570.2 in short-beaked echidna (Tachyglossus aculeatus) and 560.6 nm in platypus (Ornithorhynchus anatinus); in SWS2, λmax was 451.7 and 442.6 nm, respectively. Thus, the spectral range in echidna color vision is ~ 10 nm longer overall than in platypus. Natural selection analysis showed that the molecular evolution of monotreme color opsins is generally functionally conserved, suggesting that these taxa rely on species-specific color vision. In order to understand the usage of color vision in monotremes, we made 24-h behavioral observations of captive echidnas at warm temperatures and analyzed the resultant ethograms. Echidnas showed cathemeral activity and various behavioral repertoires such as feeding, traveling, digging, and self-grooming without light/dark environment selectivity. Halting (careful) behavior is more frequent in dark conditions, which suggests that echidnas may be more dependent on vision during the day and olfaction at night. Color vision functions have contributed to dynamic adaptations and dramatic ecological changes during the ~ 60 million years of divergent monotreme evolution. The ethogram of various day and night behaviors in captive echidnas also contributes information relevant to habitat conservation and animal welfare in this iconic species, which is locally endangered. [ABSTRACT FROM AUTHOR]

Genetic mutations resulting in abnormal colouration occur across all vertebrate groups but are considered rare, especially in mammals. Hypo-pigmentary conditions can be separated into albinism, leucism and piebaldism. The impact of colour variation on an animal's risk of predation and its ability to blend with its surroundings is widely recognised. We report our observations of a white platypus (Ornithorhynchus anatinus) in a tributary of the Gwydir River in the upper reaches of the Murray Darling Basin, New South Wales, Australia. We describe our observations in the context of historical platypus records since 1835. [ABSTRACT FROM AUTHOR]

Acoustic communication occurs in all major groups of terrestrial vertebrates, having evolved independently in early clades of mammals, birds, geckos, crocodilians and frogs, about 100–200 MYA. There is little doubt that acoustic communication was used by ancestral therian mammals, but it is ambiguous whether the reconstruction of the root of the mammalian acoustic evolutionary tree includes basal prototherian monotremes. We present here five first‐hand accounts of dove‐like cooing sounds and analyse the acoustics of three vocalization recordings for two observations of wild short‐beaked echidnas (Tachyglossus aculeatus) to quantitatively confirm acoustic communication by this species. The 'cooing' tones were quite distinctive from exhalations, wheezes and grunts, being ~0.044 s down‐sweeps from ~320 to 190 Hz, peaking at ~260 Hz, with at least one harmonic overtone. Tones occurred singly or as doublets, triplets (most common), quadruplets and quintuplets, with the leading tone typically the strongest and most broadband. We conclude that echidnas do produce vocalizations, but they are infrequent and acoustic communication is not their primary mode of communication. This unequivocal evidence for vocalization by short‐beaked echidnas resolves a long‐standing debate concerning the occurrence of acoustic communication by echidnas, which together with well‐documented vocalizations by platypus, support a very early evolution of acoustic communication amongst mammals, pre‐dating at least the common ancestor of monotremes and therian mammals. [ABSTRACT FROM AUTHOR]

Abstract Indigenous gut microbial communities (microbiota) play critical roles in health and may be especially important for the mother and fetus during pregnancy. Monotremes, such as the short‐beaked echidna, have evolved to lay and incubate an egg, which hatches in their pouch where the young feeds. Since both feces and eggs pass through the cloaca, the fecal microbiota of female echidnas provides an opportunity for vertical transmission of microbes to their offspring. Here, we characterize the gut/fecal microbiome of female short‐beaked echidnas and gain a better understanding of the changes that may occur in their microbiome as they go through pregnancy. Fecal samples from four female and five male echidnas were obtained from the Currumbin Wildlife Sanctuary in Queensland and sequenced to evaluate bacterial community structure. We identified 25 core bacteria, most of which were present in male and female samples. Genera such as Fusobacterium, Bacteroides, Escherichia‐Shigella, and Lactobacillus were consistently abundant, regardless of sex or gestation stage, accounting for 58.00% and 56.14% of reads in male and female samples, respectively. The echidna microbiome remained stable across the different gestation stages, though there was a significant difference in microbiota composition between male and female echidnas. This study is the first to describe the microbiome composition of short‐beaked echidnas across reproductive phases and allows the opportunity for this novel information to be used as a metric of health to aid in the detection of diseases triggered by microbiota dysbiosis.

In the echidna, after development in utero , the egg is laid in the pouch and incubated for 10 days. During this time, the fetuses develop an egg tooth and caruncle to help them hatch. Using rare and unprecedented access to limited echidna pre- and post-hatching tissues, development of the egg tooth and caruncle were assessed by micro-CT, histology and immunofluorescence. Unlike therian tooth germs that develop by placode invagination, the echidna egg tooth developed by evagination, similar to the first teeth in some reptiles and fish. The egg tooth ankylosed to the premaxilla, rather than forming a tooth root with ligamentous attachment found in other mammals, with loss of the egg tooth associated with high levels of activity odontoclasts and apoptosis. The caruncle formed as a separate mineralisation from the adjacent nasal capsule, and as observed in birds and turtles, the nasal region epithelium on top of the nose expressed markers of cornification. Together, this highlights that the monotreme egg tooth shares many similarities with typical reptilian teeth, suggesting that this tooth has been conserved from a common ancestor of mammals and reptiles. [Display omitted] • The echidna egg tooth is the first mammal tooth shown to develop by evagination. • The egg tooth forms rapidly, is ankylosed to the jaw and contains no enamel. • Echidnas also possess both an epithelial and mesenchymal os caruncle. [ABSTRACT FROM AUTHOR]

The sporadic reporting of fluorescent mammal discoveries has led to the trait being considered atypical. However, this perception may be misleading considering that most mammal species have not been examined. Therefore, I made a targeted attempt to assess the scope of fur fluorescence within one bioregion, the Wet Tropics of Far North Queensland, Australia. A series of 148 fresh, old and frozen wild mammals, mostly roadkill, were examined for the presence of fluorescence in their fur. Two species of monotreme, 20 of marsupial and 22 of placental were collected. Torches of various excitation wavelengths revealed that 95% of all mammal species I was able to examine from the Australian Wet Tropics had at least a low level of fluorescence visible in the fur. Fifty per cent of the mammal species had noticeably mid-to-bright fluorescent fur: 16% had strong pink fluorescence; 43% had strong blueish or other coloured fluorescence; and 9% had both. These observations recalibrate our understanding of mammalian fluorescence to be a somewhat ubiquitous feature of fur chemistry. [ABSTRACT FROM AUTHOR]

Long-beaked echidnas (Zaglossus spp.) have received less attention in the literature than Short-beaked echidnas (Tachyglossus aculeatus). Their natural history, anatomy, and physiology are poorly known. To improve our understanding of this unique group, we undertook a radiographic study of the Eastern long-beaked echidna (Zaglossus bartoni), and provide a comparative analysis of its radiographic skeletal anatomy with that of T. aculeatus. We examine conventional radiography and computed tomographic images of Zaglossus and Tachyglossus, describe the anatomical features of Zaglossus, and compare those with Tachyglossus. We provide evidence of epicoracoid overlap in echidnas, a feature not well documented in monotremes. The significance of epicoracoid overlap requires further investigation. Our study is intended as a reference for the radiographic anatomy of Z. bartoni. [ABSTRACT FROM AUTHOR]

Monotremes (echidnas and platypus) possess five X and four or five Y sex chromosomes, respectively, that evolved independently from the sex chromosomes found in therian mammals. While the platypus has obvious venomous spurs in the male, the short-beaked echidna (Tachyglossus aculeatus) lacks easily identifiable sexually dimorphic characteristics, making it difficult to sex adults out of the breeding season and almost impossible to sex juveniles or embryonic material. Here, we used restriction-site associated DNA sequencing (RADseq) to identify novel sex-specific markers in the short-beaked echidna. We identified and validated a subset of male-specific markers that can be used as a non-invasive genetic sex test for the short-beaked echidna. We also assessed how laboratory conditions, including DNA extraction protocol and number of PCR cycles, can influence the outcome of genetic sex tests. The combined use of these markers will provide a valuable toolkit for researchers, conservationists, and zoo-keepers to reliably and non-invasively determine sex in the short-beaked echidna. [ABSTRACT FROM AUTHOR]

Endogenous retroviruses (ERVs) have played an essential role in the evolution of mammals. ERV-derived genes are reported in the therians, many of which are involved in placental development; however, the contribution of the ERV-derived genes in monotremes, which are oviparous mammals, remains to be uncovered. Here, we conducted a comprehensive search for possible ERV-derived genes in platypus and echidna genomes and identified three reverse transcriptase-like genes named RTOM1 , RTOM2 , and RTOM3 clustered in the GRIP2 intron. Comparative genomic analyses revealed that RTOM1 , RTOM2 , and RTOM3 are strongly conserved and are under purifying selection between these species. These could be generated by tandem duplications before the divergence of platypus and echidna. All RTOM transcripts were specifically expressed in the testis, possibly suggesting their physiological importance. This is the first study reporting monotreme-specific de novo gene candidates derived from ERVs, which provides new insights into the unique evolution of monotremes. [ABSTRACT FROM AUTHOR]

We reviewed the many discoveries in cell biology, made since the 17th century, which have been based on red blood cells (RBCs). The advances in molecular and structural biology in the past 40 years have enabled the discovery with these cells, most notably, of the first water channel protein (WCP) called today aquaporin1 (AQP1). The main aim of our work reviewed was to examine by light and electron microscopy a very wide range of RBCs from reptiles, birds, monotremes, marsupials and placentals, in order to estimate from these images the RBC cell volume and surface area. The diffusional water permeability of the RBC membrane from these species has further been measured with a nuclear magnetic resonance (NMR) spectroscopy technique. The significance of the observed permeability of RBCs to water and possible influences on the whole body are discussed. [ABSTRACT FROM AUTHOR]

We reviewed the many discoveries in cell biology, made since the 17th century, which have been based on red blood cells (RBCs). The advances in molecular and structural biology in the past 40 years have enabled the discovery with these cells, most notably, of the first water channel protein (WCP) called today aquaporin1 (AQP1). The main aim of our work reviewed was to examine by light and electron microscopy a very wide range of RBCs from reptiles, birds, monotremes, marsupials and placentals, in order to estimate from these images the RBC cell volume and surface area. The diffusional water permeability of the RBC membrane from these species has further been measured with a nuclear magnetic resonance (NMR) spectroscopy technique. The significance of the observed permeability of RBCs to water and possible influences on the whole body are discussed.

Successful breeding of short-beaked echidnas (Tachyglossus aculeatus acanthion) occurred at Perth Zoo on eight occasions between 2007 and 2012. Here we report the methods used for monitoring and managing breeding females and their young from hatching through to weaning. Growth and development of the young during burrow-life was quantified through regular weighing and maternal care was monitored using video camera surveillance. All young hatched between early August and mid-September and were deposited in nursery burrows in October–November at 58–63 days of age at an average mass of 295 ± 64.3 g. Mothers suckled their young, on average, every 3.3 ± 1.1 days. Young first emerged from their nursery burrow from mid-January into February at an average 169 ± 21 days of age and weighing 1674 ± 511 g, and reached 3 kg in mass at 348 ± 97 days of age. Sexual maturity of two female offspring was attained at 4 years of age. Our observations of maternal care and development of the captive-bred young are consistent with published observations made on wild echidnas. We suggest that important factors for the successful rearing of captive-bred echidnas are enclosure set-up, daily monitoring, combined with a suitably designed and managed nursery burrow that provides a suitable substrate and microenvironment. Eight short-beaked echidnas were successfully bred and reared to independence at Perth Zoo between 2007 and 2012. Detailed information was gathered on the development of the young during nursery burrow life and weaning through to 2 years of age, filling important knowledge gaps in this species. Our study provides insights to support the rearing of orphaned wild echidnas for rehabilitation as well as a foundation of knowledge to support development of similar important wildlife breeding programs. Photograph by Arthur Ferguson. [ABSTRACT FROM AUTHOR]

The short-beaked echidna is an iconic Australian animal and the most-widespread native mammal, inhabiting diverse environments. The cryptic nature of echidnas has limited research into their ecology in most areas; however, from the well-researched and endangered Kangaroo Island echidna population, we understand that the threats include habitat loss, roads, and invasive species. To obtain more information about echidnas Australia-wide, we established the Echidna Conservation Science Initiative (EchidnaCSI) citizen science project. EchidnaCSI calls on members of the public to submit photographs of wild echidnas and learn to identify and collect echidna scats for molecular analysis. To facilitate participation, we developed a smartphone application as well as ongoing social and traditional media activities and community events. In 3 y, more than 9,000 members of the public have downloaded the EchidnaCSI app, collecting 400 scats and submitting over 8,000 sightings of echidnas from across Australia. A subset of submitted scat samples were subjected to DNA extraction and PCR, which validated the approach of using citizen science for scat collection and viability for molecular analysis. To assess the impact of the project through public participation, we surveyed our participants (n = 944) to understand their demographics and motivations for engagement. Survey results also revealed that EchidnaCSI served as a gateway into citizen science more generally for many participants. EchidnaCSI demonstrates the potential for using citizen science approaches to collect high-quality data and material from a cryptic species over a very large geographic area and the considerable engagement value of citizen science research. [ABSTRACT FROM AUTHOR]

Echidnas are commonly known as 'spiny ant-eaters', but long-beaked echidnas (Zaglossus spp.) do not eat ants, whereas short-beaked echidnas (Tachyglossus aculeatus) eat other invertebrates as well as ants. The differences in skull morphology between short- and long-beaked echidnas are related to the differences in their diets, and I tested the hypothesis that there would be differences in beak length of short-beaked echidnas from populations with different diets. Published data on diet from echidnas from different parts of Australia show that echidnas from arid and semi-arid areas (subspecies acanthion) and Kangaroo Island (subspecies multiaculeatus) principally eat ants and termites, whereas the main dietary items of echidnas from south-eastern Australia (subspecies aculeatus) and Tasmania (subspecies setosus) are ants and scarab larvae. Using museum specimens and photographs I measured skull dimensions on echidnas from different parts of Australia: acanthion and multiaculeatus have narrower skulls and shorter beaks than aculeatus and setosus , with setosus being the only Australian subspecies where beak length exceeds cranium length. Australian short-beaked echidnas fall into two groups: aculeatus and setosus from the wetter east and south-east, which eat ant and scarab larvae, and the arid and semi-arid zone acanthion and multiaculeatus , with shorter, narrower skulls, and which eat ants and termites. Echidnas occur all over Australia, but echidnas from different regions vary greatly in the length of the spines and hair. This paper shows there are also big differences in beak length. Tasmanian echidnas have the longest beaks, whereas arid zone echidnas have very short beaks. Beak length is related to diet and feeding behaviour: longer beaks are better suited to probing for scarab larvae, while short beaks are better for ploughing through the soil for ants and termites. Diet, beak length and claw lengths divide Australian echidnas into two groups. [ABSTRACT FROM AUTHOR]

The peer-reviewed Australian Zoologist, first published in 1914, is Australia's longest-lived zoological journal. Its publication history shows changes in the zoological topics covered over the last 100 years, including the animals studied, characteristics of the authors and readership, and the influence of the databases used to study the journal on information retrieval. Searches in different databases retrieved different numbers of papers; Scopus (including secondary documents not in the database but cited by documents that are in the database) was the most comprehensive. Although authors from 22 countries contributed papers over the history of the Australian Zoologist, over 90% of authors were Australian. Most international authors came from the USA, the UK, Canada and New Zealand. Approximately two-thirds of authors citing Australian Zoologist were Australian-based, but there were still 10 or more authors from each of thirty-four other countries citing Australian Zoologist: while regional, the journal has an international profile. Highly cited papers in Australian Zoologist had high mean Scopus percentile ranks (20th century 83.9, 21st century 73.7), indicating that in comparison to their fields globally, these papers are used well above average. Considering all papers published in Australian Zoologist, over time the proportion of papers in the categories 'Biodiversity & Conservation' and 'Environmental Sciences & Ecology' rose significantly, reflecting the increased research in these areas. Between 2013 and 2019, when relevant metrics are available in Scopus, Australian Zoologist declined in no metric measured while improving significantly in CiteScore, Highest Percentile, and % Cited, indicating increasing references to Australian Zoologist papers by other peer-reviewed publications. Between 2010 and 2019, 2.1% of Australian Zoologist papers were ranked within the top 10% in their fields globally, based on citation impact. Authors considering publishing in Australian Zoologist should note that longer papers are acceptable, colour imagery (including photographs) is encouraged, the journal is visible in major databases, it is cited internationally and there are no page charges. [ABSTRACT FROM AUTHOR]

Botryomycosis is a chronic bacterial infection of the skin and viscera caused by nonbranching bacteria such as Staphylococcus spp. It results in the formation of chronic, suppurative and often granulomatous lesions that may resemble multiple abscesses. It has been diagnosed worldwide in both humans and animals. It is a rare disease, usually requiring surgical excision combined with long‐term antibiotics to achieve a good resolution. A wild echidna (Tachyglossus aculeatus) was presented with a soft tissue mass at the base of the right distal beak with multiple discharging fistulas arising from it. The mandible appeared to be shortened and deviated to the right, and the animal was unable to close its beak. The echidna was in poor body condition and was euthanased on welfare grounds. Histopathology of the lesions demonstrated the classical botryoid lesions with the characteristic Splendore‐Hoeppli reaction surrounding the bacterial colonies, in a background of extensive granulation tissue. Radiographs revealed mild mandibular osteomyelitis, yet haematology and biochemistry results were nonspecific. This disease has not previously been reported in a wild monotreme. [ABSTRACT FROM AUTHOR]

Distribution data on platypus populations within the Greater Brisbane region is currently lacking, limiting our understanding of their population status. We report 4 years of platypus environmental DNA data from waterways in this region and compare them to historical observational records from 1990 to 2016 to determine any changes to their distribution. Twenty-one of the 54 eDNA sampled waterways were sampled multiple times and had records of previous platypus presence. Five of these 21 repeatedly sampled waterways (24%) did not have evidence of platypus presence, based on eDNA. This raises the concern that platypuses may no longer inhabit these waterways. We hope this study encourages further investigations on platypus to identify the extent of their decline within the region, along with possible broader state-wide review of their conservation status for future protection. [ABSTRACT FROM AUTHOR]

Monotremes diverged from therian mammal ancestors approximately 184 million years ago and have a number of novel reproductive characteristics. One in particular is their penile morphology. There are differences between echidna and platypus phalluses, but both are somewhat similar in structure to the reptilian phallus. The echidna penis consists of 4 rosette glans, each of which contains a termination of the quadrifurcate urethra, but it appears that only 2 of the 4 glans become erect at any one time. Despite this, only a few historical references describe the structure of the echidna penis and none provides an explanation for the mechanisms of unilateral ejaculation. This study confirmed that the echidna penis contains many of the same overall structures and morphology as other mammalian penises and a number of features homologous with reptiles. The corpus cavernosum is well supplied with blood, extends up to the base of the glans penis and is primarily responsible for erection. However, the echidna possesses 2 distinct corpora spongiosa separated by a septum, each of which surround the urethra only distal to the initial urethral bifurcation in the glans penis. Together with the bifurcation of the main penile artery, this provides a mechanism by which blood flow could be directed to only one corpus spongiosum at a time to maintain an open urethra that supplies 2 of the 4 glans to facilitate unilateral ejaculation. [ABSTRACT FROM AUTHOR]

Comparing the genes expressed at the maternal-fetal interface in different species helps to pinpoint those that contribute to a healthy pregnancy by regulating the activity of the immune system.

River regulation has extensively changed the ecology and hydrology of rivers worldwide, particularly downstream of dams, affecting the viability of freshwater species. The platypus (Ornithorhynchus anatinus) is a semiaquatic monotreme, endemic to eastern Australia, with a distribution overlapping Australia's most regulated rivers.Dams and changes to flow regimes have affected critical platypus habitat, yet our understanding of the impacts of these threatening processes on platypus ecology remains poor. Over a period of 3 years (2016–2018), platypuses were surveyed across three regions (Upper Murray, Snowy, and Border river regions), above and below large dams, and in adjacent unregulated rivers, comparing captures, demographics, abundances, and densities. We hypothesized that platypus captures and abundances would be lower downstream of dams, owing to altered flow regimes that have secondary impacts on the demographics of these populations.In the Upper Murray Rivers region, captures were significantly lower in the Mitta Mitta River below Dartmouth Dam, compared with captures upstream of the dam and the unregulated Ovens River, probably reflecting significant alteration to the seasonality and temperature of flows caused by the dam. Conversely, there were no significant differences in captures or abundance and density estimates above and below the dams in the Snowy or Border river regions, where the extent of regulation was less severe, probably as a result of restoration efforts in recent years on some rivers.Low proportions of juveniles on the Snowy River and Mitta Mitta River downstream of the dams, compared with upstream, raises concerns of other impacts of altered flow regimes to platypus breeding success and juvenile survival, given the sensitivity of juveniles to unseasonably high flows.The results highlighted the potential impact of river regulation, with direct implications for the management of regulated rivers, providing opportunities to mitigate impacts through improved management of the seasonality and temperature of flows, to the benefit of platypuses and other freshwater species. [ABSTRACT FROM AUTHOR]

The developmental origins and evolutionary histories of cell types, tissues, and organs contribute to the ways in which their dysfunction produces disease. In mammals, the nature, development and evolution of maternal-fetal interactions likely influence diseases of pregnancy. Here we show genes that evolved expression at the maternal-fetal interface in Eutherian mammals play essential roles in the evolution of pregnancy and are associated with immunological disorders and preterm birth. Among these genes is HAND2, a transcription factor that suppresses estrogen signaling, a Eutherian innovation allowing blastocyst implantation. We found dynamic HAND2 expression in the decidua throughout the menstrual cycle and pregnancy, gradually decreasing to a low at term. HAND2 regulates a distinct set of genes in endometrial stromal fibroblasts including IL15, a cytokine also exhibiting dynamic expression throughout the menstrual cycle and gestation, promoting migration of natural killer cells and extravillous cytotrophoblasts. We demonstrate that HAND2 promoter loops to an enhancer containing SNPs implicated in birth weight and gestation length regulation. Collectively, these data connect HAND2 expression at the maternal-fetal interface with evolution of implantation and gestational regulation, and preterm birth.

The platypus is a cryptic mammal that inhabits freshwater streams and rivers of eastern Australia. Tracking the movements of wild platypuses has been notoriously difficult due to the animals' morphology and methodological limitations. Knowledge of fine‐scale movements and interactions among individuals remain particularly poorly understood, as do responses to changes in hydrology.We tracked movements of 15 platypuses (six females, nine males) downstream of the Jindabyne Dam on the Snowy River, using externally attached acoustic transmitters (September–November 2017), to assess spatio‐temporal activity patterns among individuals and changes in movement and activity before and after an environmental flushing flow. As the study took place during the breeding season, we expected to observe overlap in area of activity among males and females, but not among males due to increased territoriality during these months. We also anticipated that a large flow event would impact their activity and foraging behaviour, possibly displacing platypuses downstream.Overlaps in area of activity and temporal co‐occurrence within a pool varied among individuals, with two resident males exhibiting some spatial overlap of activity and varying temporal co‐occurrence, despite tracking during the breeding season. All six tracked females were captured in the same pool and appeared to be residents, possibly highlighting preferences for certain habitats during the breeding months.We found no evidence that the movements of adult platypuses were affected by an environmental flushing flow, with no significant changes to area of activity, number of detections, or daily range of movements. However, foraging duration increased in the week after the flow, possibly associated with increased prey availability.These findings suggest that territoriality between males during and after the breeding season may depend on platypus density and resource availability and that pools with high resource availability may support several breeding females. [ABSTRACT FROM AUTHOR]

All mammals are characterized by the ability of females to produce milk. Marsupial (metatherian) and monotreme (prototherian) young are born in a highly altricial state and rely on their mother’s milk for the first part of their life. Here we review the role and importance of milk in marsupial and monotreme development. Milk is the primary source of sustenance for young marsupials and monotremes and its composition varies at different stages of development. We applied nutritional geometry techniques to a limited number of species with values available to analyze changes in macronutrient composition of milk at different stages. Macronutrient energy composition of marsupial milk varies between species and changes concentration during the course of lactation. As well as nourishment, marsupial and monotreme milk supplies growth and immune factors. Neonates are unable to mount a specific immune response shortly after birth and therefore rely on immunoglobulins, immunological cells and other immunologically important molecules transferred through milk. Milk is also essential to the development of the maternal-young bond and is achieved through feedback systems and odor preferences in eutherian mammals. However, we have much to learn about the role of milk in marsupial and monotreme mother-young bonding. Further research is warranted in gaining a better understanding of the role of milk as a source of nutrition, developmental factors and immunity, in a broader range of marsupial species, and monotremes.

The novel mammalian jaw joint, known in humans as the temporomandibular joint or TMJ, is cushioned by a fibrocartilage disc. This disc is secondarily absent in therian mammals that have lost their dentition, such as giant anteaters and some baleen whales. The disc is also absent in all monotremes. However, it is not known if the absence in monotremes is secondary to the loss of dentition, or if it is an ancestral absence. We use museum held platypus and echidna histological sections to demonstrate that the developing monotreme jaw joint forms a disc primordium that fails to mature and become separated from the mandibular condyle. We then show that monotreme developmental anatomy is similar to that observed in transgenic mouse mutants with reduced cranial musculature. We therefore suggest that the absence of the disc on monotremes is a consequence of the changes in jaw musculature associated with the loss of adult teeth. Taken together, these data indicate that the ancestors of extant monotremes likely had a jaw joint disc, and that the disc evolved in the last common ancestor of all mammals.

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 24 h 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. This study investigates the maternal care given to platypus nestlings and describes a technique to study animals in a burrow. Platypus nestlings develop quickly over four months. The mother has high energy requirements for lactation, increasing her food intake by double towards the end. Weaning occurred rapidly at the time of emergence. This paper is the first to describe the growth and development of platypus nestlings at known ages. Photograph by Jessica Thomas. [ABSTRACT FROM AUTHOR]

All mammals are characterized by the ability of females to produce milk. Marsupial (metatherian) and monotreme (prototherian) young are born in a highly altricial state and rely on their mother's milk for the first part of their life. Here we review the role and importance of milk in marsupial and monotreme development. Milk is the primary source of sustenance for young marsupials and monotremes and its composition varies at different stages of development. We applied nutritional geometry techniques to a limited number of species with values available to analyze changes in macronutrient composition of milk at different stages. Macronutrient energy composition of marsupial milk varies between species and changes concentration during the course of lactation. As well as nourishment, marsupial and monotreme milk supplies growth and immune factors. Neonates are unable to mount a specific immune response shortly after birth and therefore rely on immunoglobulins, immunological cells and other immunologically important molecules transferred through milk. Milk is also essential to the development of the maternal-young bond and is achieved through feedback systems and odor preferences in eutherian mammals. However, we have much to learn about the role of milk in marsupial and monotreme mother-young bonding. Further research is warranted in gaining a better understanding of the role of milk as a source of nutrition, developmental factors and immunity, in a broader range of marsupial species, and monotremes. [ABSTRACT FROM AUTHOR]

Many small- and medium-sized mammals dig for their food. This activity potentially affects soil condition and fertility. Digging is well developed especially in Australian mammals, many of which have recently become rare or extinct. We measured the effects of digging by mammals on soil in a Tasmanian temperate dry sclerophyll forest with an intact mammal community. The density of diggings was 5812 ha−1, affecting 11% of the forest floor. Diggings were created at a rate of around 3113 diggings ha−1 yr−1, disturbing 6.5% of the forest floor and displacing 7.1 m3 ha−1 of soil annually. Most diggings were made by eastern bettongs (Bettongia gaimardi) and short-beaked echidnas (Tachyglossus aculeatus). Many (approx. 30%) fresh diggings consisted of re-excavations of old diggings. Novel diggings displaced 5 m3 ha yr−1 of soil. Diggings acted as traps for organic matter and sites for the formation of new soil, which had higher fertility and moisture content and lower hardness than undisturbed topsoil. These effects on soil fertility and structure were strongest in habitats with dry and poor soil. Creation of fine-scaled heterogeneity by mammals, and amelioration of dry and infertile soil, is a valuable ecosystem service that could be restored by reintroduction of digging mammals to habitats from which they have declined or gone extinct.

Indigenous gut microbial communities (microbiota) play critical roles in health and may be especially important for the mother and fetus during pregnancy. Monotremes, such as the short-beaked echidna, have evolved to lay and incubate an egg, which hatches in their pouch where the young feeds. Since both feces and eggs pass through the cloaca, the fecal microbiota of female echidnas provides an opportunity for vertical transmission of microbes to their offspring. Here, we characterize the gut/fecal microbiome of female short-beaked echidnas and gain a better understanding of the changes that may occur in their microbiome as they go through pregnancy. Fecal samples from four female and five male echidnas were obtained from the Currumbin Wildlife Sanctuary in Queensland and sequenced to evaluate bacterial community structure. We identified 25 core bacteria, most of which were present in male and female samples. Genera such as Fusobacterium, Bacteroides, Escherichia-Shigella, and Lactobacillus were consistently abundant, regardless of sex or gestation stage, accounting for 58.00% and 56.14% of reads in male and female samples, respectively. The echidna microbiome remained stable across the different gestation stages, though there was a significant difference in microbiota composition between male and female echidnas. This study is the first to describe the microbiome composition of short-beaked echidnas across reproductive phases and allows the opportunity for this novel information to be used as a metric of health to aid in the detection of diseases triggered by microbiota dysbiosis., (© 2023 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

Echidnas are egg‐laying mammals found across Australia, and in Tasmania they hibernate, resulting in a most unusual mating system: males enter hibernation in late summer–early autumn and arouse in late autumn–early winter to mate, although females are still hibernating. Groups of males compete for matings and both males and females mate with multiple partners. Females that mate early return to hibernation even when pregnant, and males continue to mate with pregnant females. We asked to what extent can the bizarre combination of behavioural and physiological features that characterize reproduction of Tasmanian echidnas be attributed to their phylogeny, and how much is a consequence of their ecology?To understand the interaction between energetics and the echidna mating system in determining the timing of echidna hibernation, we analysed data from an 18‐year study of a wild population of Tasmanian echidnas (Tachyglossus aculeatus setosus)Males in best condition arouse earliest and seek out suitable females, and females that mate early in the mating season re‐enter hibernation while pregnant.Competition between males drives early mating and while mating with males in the best condition could be advantageous for females and their young, egg‐laying in winter is potentially disadvantageous, and post‐mating hibernation by females is a means of delaying hatching of young until environmental conditions are more favourable. This post‐mating hibernation by females is usually disrupted by males which mate with them although they are already pregnant.Comparisons with other echidna populations suggest that a decreased activity period due to hibernation has not increased male–male competition.Similar competition between groups of males for access to females is seen in chlamyphorid armadillos, which occupy a similar ecological niche to echidnas. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Tachyglossus aculeatus (Shaw, 1792) is a monotreme commonly called the short-beaked echidna. Although considered Australia's most common native mammal because of its continent-wide distribution, its population numbers everywhere are low. It is easily distinguished from all other native Australian mammals because of its spine-covered body, hairless beak, and unique "rolling" gait. The five subspecies, one of which is found in Papua New Guinea, show variations in fur density, spine diameter, length, and number of grooming claws. The Kangaroo Island short-beaked echidna Tachyglossus aculeatus multiaculeatus is listed as "Endangered" but all other Tachyglossus are listed as "Least Concern" in the 2016 International Union for Conservation of Nature and Natural Resources Red List. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We present data from an 18-year study of a wild population of Tasmanian echidnas, which show that the presence of spurs in an adult are a reliable indicator of sex, and that there is a slight but significant sexual dimorphism in size, with a male to female mass ratio of 1.1. Minimum age at first breeding in the wild for Tasmanian echidnas was 5 years, as has been found on Kangaroo Island, compared with 3 years in captive echidnas. It is often assumed that although the echidna is distributed throughout Australia, New Guinea and off-shore islands that all aspects of its basic biology are the same in all populations, but comparisons of our results with data from other populations suggest that there may be differences in size and sexual dimorphism. [ABSTRACT FROM AUTHOR]

Receptors of the leukocyte receptor cluster (LRC) play a range of important functions in the human immune system. However, the evolution of the LRC remains poorly understood, even in m\ammals not to mention nonmammalian vertebrates. We conducted a comprehensive bioinformatics analysis of the LRC-related genes in the publicly available genomes of six species that represent eutherian, marsupial, and monotreme lineages of mammals. As a result, the LRCs of African elephant and armadillo were characterized, two new genes, IGSF1 and A1BG , were attributed to the LRC of eutherian mammals, the LRC gene content was substantially extended in the short-tailed opossum and Tasmanian devil and, finally, four LRC genes were identified in the platypus genome. These findings have for the first time provided a solid basis for inference of the LRC phylogeny across mammals. Our analysis suggests that the mammalian LRC family likely derived from two ancestral genes, which evolved in a lineage-specific manner by expansion/contraction, extensive exon shuffling, and sequence divergence. The striking structural and functional diversity of eutherian LRC molecules appears largely lineage specific. The only family member retained in all the three mammalian lineages is a collagen-binding receptor OSCAR. Strong sequence conservation of a transmembrane domain known to associate with FcRγ suggests an adaptive role of this domain subtype in the LRC evolution. [ABSTRACT FROM AUTHOR]

The platypus (Ornithorhynchus anatinus) is an egg-laying monotreme mammal whose ancestors diverged ∼166 million years ago from the evolutionary pathway that eventually gave rise to both marsupial and eutherian mammals. Consequently, its genome is an extraordinary amalgam of both ancestral reptilian and derived mammalian features. To gain insight into the evolution of mammalian pluripotency, we have generated induced pluripotent stem cells from the platypus (piPSCs). Deep sequencing of the piPSC transcriptome revealed that piPSCs robustly express the core eutherian pluripotency factors POU5F1/OCT4, SOX2, and NANOG. Given the more extensive role of SOX3 over SOX2 in avian pluripotency, our data indicate that between 315 and 166 million years ago, primitive mammals replaced the role of SOX3 in the vertebrate pluripotency network with SOX2. DAX1/NR0B1 is not expressed in piPSCs and an analysis of the platypus DAX1 promoter revealed the absence of a proximal SOX2-binding DNA motif known to be critical for DAX1 expression in eutherian pluripotent stem cells, suggesting that the acquisition of SOX2 responsiveness by DAX1 has facilitated its recruitment into the pluripotency network of eutherians. Using the RNAseq data, we were also able to demonstrate that in both fibroblasts and piPSCs, the expression ratio of X chromosomes to autosomes (X1–5 X1–5:AA) is approximately equal to 1, indicating that there is no upregulation of X-linked genes. Finally, the RNAseq data also allowed us to explore the process of X-linked gene inactivation in the platypus, where we determined that for any given gene, there is no preference for silencing of the maternal or paternal allele; that is, within a population of cells, the silencing of X-linked genes is not imprinted. [ABSTRACT FROM AUTHOR]

Although evolutionary transformation of the pectoral girdle and forelimb appears to have had a profound impact on mammalian locomotor and ecological diversity, both the sequence of anatomical changes and the functional implications remain unclear. Monotremes can provide insight into an important stage of this evolutionary transformation, due to their phylogenetic position as the sister-group to therian mammals and their mosaic of plesiomorphic and derived features. Here we build a musculoskeletal computer model of the echidna pectoral girdle and forelimb to estimate joint ranges of motion (ROM) and muscle moment arms (MMA)—two fundamental descriptors of biomechanical function. We find that the echidna's skeletal morphology restricts scapulocoracoid mobility and glenohumeral flexion–extension compared with therians. Estimated shoulder ROMs and MMAs for muscles crossing the shoulder indicate that morphology of the echidna pectoral girdle and forelimb is optimized for humeral adduction and internal rotation, consistent with limited in vivo data. Further, more muscles act to produce humeral long-axis rotation in the echidna compared to therians, as a consequence of differences in muscle geometry. Our musculoskeletal model allows correlation of anatomy and function, and can guide hypotheses regarding function in extinct taxa and the morphological and locomotor transformation leading to therian mammals.

The dietary preference of most crocodilians is generally thought to be fairly broad. However, the head morphology of slender-snouted crocodilians limits their ability to process large and complex prey. The slender-snouted Australian freshwater crocodile is known to be a dietary specialist consuming small aquatic prey, particularly aquatic arthropods and fish. Here, we report observations of predation events by Australian freshwater crocodiles on medium- and large-sized mammals in the Kimberley region of Western Australia including macropods, a large rodent and an echidna. We discuss the significance of our observations from an ecological and morphological perspective and propose that terrestrial mammalian prey may be a seasonally important prey item for some populations of freshwater crocodiles. [ABSTRACT FROM AUTHOR]