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The platypus (Ornithorhynchus anatinus) is one of the world’s most evolutionarily distinct mammals, one of five extant species of egg-laying mammals, and the only living species within the family Ornithorhynchidae. Modern platypuses are endemic to eastern mainland Australia, Tasmania, and adjacent King Island, with a small introduced population on Kangaroo Island, South Australia, and are widely distributed in permanent river systems from tropical to alpine environments. Accumulating knowledge and technological advancements have provided insights into many aspects of its evolutionary history and biology but have also raised concern about significant knowledge gaps surrounding distribution, population sizes, and trends. The platypus’ distribution coincides with many of Australia’s major threatening processes, including highly regulated and disrupted rivers, intensive habitat destruction, and fragmentation, and they were extensively hunted for their fur until the early 20th century. Emerging evidence of local population declines and extinctions identifies that ecological thresholds have been crossed in some populations and, if threats are not addressed, the species will continue to decline. In 2016, the IUCN Red Listing for the platypus was elevated to “Near Threatened,” but the platypus remains unlisted on threatened species schedules of any Australian state, apart from South Australia, or nationally. In this synthesis, we review the evolutionary history, genetics, biology, and ecology of this extraordinary mammal and highlight prevailing threats. We also outline future research directions and challenges that need to be met to help conserve the species.

The platypus ( Ornithorhynchus anatinus ) is known to be vulnerable to drowning in enclosed traps used to capture freshwater crayfish such as yabbies ( Cherax spp.). To help quantify the degree of risk posed by such traps, we carried out 113 trials in Victorian streams and larger New South Wales rivers to assess the platypus’s ability to escape from standard opera house traps (OH), a second commercially available enclosed trap design (closed-top pyramid traps, CTP), and opera house traps that had been modified by adding an opening in the roof (MOH). All 10 of the animals tested in OH failed to find an exit in the period allowed. In contrast, 82% of subjects tested in CTP ( n = 45) and 83% of those tested in MOH ( n = 58) escaped from traps within 2 min. Victorian animals took significantly less time to escape from traps (CTP, mean = 31 s; MOH, 33 s) than those tested in New South Wales (CTP, mean = 55 s; MOH, 53 s). In addition, juveniles were less likely than adults to escape from CTP and MOH in a timely manner. The results of trials comparing the number and size of yabbies captured in Victorian farm ponds indicate that MOH should at least equal and potentially exceed the performance of OH when used to harvest yabbies for human consumption.

The platypus (Ornithorhynchus anatinus) is an evolutionarily distinct mammal, endemic to Australian freshwaters. Many aspects of its ecology and life-history, including detailed understanding of movements, are poorly known, hampered by its cryptic and mainly nocturnal habits and small numbers. We effectively trialled intraperitoneal implanted acoustic transmitters in nine platypuses in the Severn River (NSW), Australia, as a potential approach for studying movements in this challenging species. We tracked platypus movements over six months, at fine and broad spatial scales, using an array of acoustic sensors. Over six months (March-August 2016), four of five adult platypuses (two females\three males) maintained localized movements (average monthly maximums 0.37 km ± 0.03 sd), while one adult, one sub-adult, and one juvenile (males) moved further: average monthly maxima 1.2 km ± 2.0 sd, 0.9 km ± 0.6 sd, 4.5 km ± 5.9 sd, respectively. The longest recorded movement was by a male adult, covering 11.1 km in three days and travelling a maximum distance of about 13 km between records. Only one implanted animal was not detected immediately after release, indicative of transmission failure rather than an adverse event. High cumulative daily movements (daily 1.9 km ± 0.8 sd) indicated high metabolic requirements, with implications for previous estimates of platypus abundances and carrying capacities, essential for effective conservation. This novel approach offers new avenues to investigate relating to mating, nesting, and intraspecific competition behaviours and their temporal and spatial variation.

The platypus is an egg-laying mammal which, alongside the echidna, occupies a unique place in the mammalian phylogenetic tree. Despite widespread interest in its unusual biology, little is known about its population structure or recent evolutionary history. To provide new insights into the dispersal and demographic history of this iconic species, we sequenced the genomes of 57 platypuses from across the whole species range in eastern mainland Australia and Tasmania. Using a highly-improved reference genome, we called over 6.7M SNPs, providing an informative genetic data set for population analyses. Our results show very strong population structure in the platypus, with our sampling locations corresponding to discrete groupings between which there is no evidence for recent gene flow. Genome-wide data allowed us to establish that 28 of the 57 sampled individuals had at least a third-degree relative amongst other samples from the same river, often taken at different times. Taking advantage of a sampled family quartet, we estimated thede novomutation rate in the platypus at 7.0×10−9/bp/generation (95% CI 4.1×10−9− 1.2×10−8/bp/generation). We estimated effective population sizes of ancestral populations and haplotype sharing between current groupings, and found evidence for bottlenecks and long-term population decline in multiple regions, and early divergence between populations in different regions. This study demonstrates the power of whole-genome sequencing for studying natural populations of an evolutionarily important species.

Monotremes (platypus and echidna) are the descendants of the oldest ancestor of all extant mammals distinguished from other mammals by mode of reproduction. Monotremes lay eggs following a short gestation period and after an even briefer incubation period, altricial hatchlings are nourished over a long lactation period with milk secreted by nipple-less mammary patches located on the female’s abdomen. Milk is the sole source of nutrition and immune protection for the developing young until weaning. Using transcriptome and mass spectrometry analysis of milk cells and milk proteins, respectively, a novel Monotreme Lactation Protein (MLP) was identified as a major secreted protein in milk. We show that platypus and short-beaked echidna MLP genes show significant homology and are unique to monotremes. The MLP transcript was shown to be expressed in a variety of tissues; however, highest expression was observed in milk cells and was expressed constitutively from early to late lactation. Analysis of recombinant MLP showed that it is an N-linked glycosylated protein and biophysical studies predicted that MLP is an amphipathic, α-helical protein, a typical feature of antimicrobial proteins. Functional analysis revealed MLP antibacterial activity against both opportunistic pathogenic Staphylococcus aureus and commensal Enterococcus faecalis bacteria but showed no effect on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Salmonella enterica. Our data suggest that MLP is an evolutionarily ancient component of milk-mediated innate immunity absent in other mammals. We propose that MLP evolved specifically in the monotreme lineage supporting the evolution of lactation in these species to provide bacterial protection, at a time when mammals lacked nipples.

Dispersal patterns can have a major impact on the dynamics and viability of populations, and understanding these patterns is crucial to the conservation and management of a species. In this study, patterns of sex-biased dispersal and waterway/overland dispersal are investigated in the endemic Australian platypus, Ornithorhynchus anatinus, a semi-aquatic monotreme. Analyses of over 750 individuals from south-eastern Australia at 13 microsatellite loci and two mitochondrial genes, cytochrome b and cytochrome oxidase subunit II, provide genetic insight into dispersal patterns. For the first time, platypuses of western Victoria are shown to be genetically distinct from other populations of the mainland. Despite distinct morphological differentiation either side of the Great Dividing Range, populations remain genetically similar between coastal and inland areas suggesting gene flow is likely to occur across these ranges. Landscape genetic analyses indicate variability in dispersal patterns between Victorian and Tasmanian platypuses with a greater avoidance of overland travel indicated in Victoria compared to Tasmania. Females appear to remain within their natal area or return to breed, maintaining greater genetic structure in maternally inherited mitochondrial DNA in comparison to nuclear DNA and sharing genetic similarity within a short river distance (i.e. ≤1.4 km). The results of this study provide a valuable spatial framework for the management of wild platypus populations within south-eastern Australia and a baseline for future monitoring of populations that are likely to be impacted by environmental and anthropogenic change.

The diet of the platypus Ornithorhynchus anatinus was studied by examination of material collected from the cheek pouches of animals captured while foraging in streams in Kangaroo Valley, NSW, Australia. Platypuses consumed benthic invertebrates from 55 families in 16 orders, with virtually no prey being derived from the terrestrial environment. We also sampled invertebrates in pool, riffle and stream edge habitats to identify where prey were obtained. Invertebrates in the diet were most similar to those collected along stream edges and in pools compared with the faster-flowing riffles, suggesting that platypuses focused their foraging activities largely in these deeper water habitats. Although there was no seasonality in the assemblage structure of macroinvertebrates, the diet of platypuses varied between seasons, notably between winter and summer, suggesting that some dietary selectivity is seasonal. Dietary differences between the sexes were not detected. Overall, our results suggest that some dietary selection occurs in the platypus with respect to both foraging habitat and season. Seasonal selectivity may reflect different metabolic demands on platypuses at different times of the year. In contrast, habitat selectivity may reflect difficulty of prey access and risk of prey escape in fast-flowing riffles, higher energy costs and risk of predation associated with exploiting this habitat, and prey avoidance responses that are more rapid in the shallow riffles than in the deeper water pools and stream edges. These alternatives await evaluation by future research.

Knowledge of the life-history and population dynamics of Australia’s iconic and evolutionarily distinct platypus (Ornithorhynchus anatinus) remains poor. We marked-recaptured 812 unique platypuses (total 1,622 captures), over four decades (1973–2014) in the Shoalhaven River, Australia. Strong sex-age differences were observed in life-history, including morphology and longevity. Apparent survival of adult females (Φ = 0.76) were higher than adult males (Φ = 0.57), as in juveniles: females Φ = 0.27, males Φ = 0.13. Females were highly likely to remain in the same pool (adult: P = 0.85, juvenile: P = 0.88), while residency rates were lower for males (adult: P = 0.74, juvenile: P = 0.46). We combined survival, movement and life-histories to develop population viability models and test the impact of a range of life-history parameters. While using estimated apparent survival produced unviable populations (mean population growth rate r = −0.23, extinction within 20 years), considering residency rates to adjust survival estimates, indicated more stable populations (r = 0.004, p = 0.04 of 100-year extinction). Further sensitivity analyses highlighted adult female survival and overall success of dispersal as most affecting viability. Findings provide robust life-history and viability estimates for a difficult study species. These could support developing large-scale population dynamics models required to underpin a much needed national risk assessment for the platypus, already declining in parts of its current distribution.

The platypus (Ornithorhynchus anatinus) is an Australian icon. It is an integral part of the biodiversity of many eastern Australian freshwater ecosystems and is protected by legislation in all States in which it occurs. Its conservation is of considerable importance not only because of its unique features, status and niche but also because it is the only living representative of a significant lineage of platypus-like animals with a 60 million year fossil history. As a result of its specific habitat requirements it is affected by many of the widely recognised threatening processes operating in Australian limnological systems. In spite of these threatening processes, the species has continued to inhabit and reproduce in considerably degraded environments. The present overall distribution of the platypus appears to be little different from pre-European times. There are, however, now almost certainly no naturally occurring populations in South Australia, where it once occurred, and its distribution has apparently shrunk in the lower reaches of the Murray and Murrumbidgee River systems in Victoria and New South Wales. Despite being considered common throughout its current distribution its abundance is not readily measured and therefore its future conservation status is not easily predicted. Several studies have reported fragmentation of platypus distribution within individual river systems. This has been attributed to poor land management practices associated with stream bank erosion, loss of riparian vegetation and channel sedimentation. There is currently also evidence for adverse effects of river regulation and impoundments, introduced species, poor water quality, fisheries by-catch mortality and disease on platypus populations, but none of these has been well studied. Investigations of these aspects of the species’ biology and interaction with human activities are research priorities, while management priorities include the development and implementation of strategies aimed at reducing the effects of these human activities on the platypus and its habitat.

The platypus (Ornithorhynchus anatinus) occupies a wide range of aquatic habitats, feeding mainly on benthic macroinvertebrates. In this study, we investigated how flow affects platypus reproduction in the unregulated upper Shoalhaven River in rural New South Wales. In a mainly dry period, the population occurred at relatively high density (12.4 animals km–1) and was strongly female-biased (84% of resident animals); mean annual loss and recruitment of resident females were respectively estimated to be 12% and 14%. Percentage lactation was 17–71% (n = 23 years), and annual reproductive success (defined as the mean number of juveniles captured per adult/subadult female from February to April) varied from 0 to 1.5 juveniles female–1 (n = 21 years). A significant positive linear relationship was evident between percentage lactation and antecedent discharge in the five months before breeding (March–July) and a positive curvilinear relationship was evident between percentage lactation and mean litter size. Conversely, reproductive success was compromised by high poststorm discharge in the period when juveniles are confined to a nesting burrow, especially from late November to early January. The relationships identified in our study between flow and reproduction also appear to apply to platypus populations occupying urban streams in Victoria, suggesting that they may be widely relevant to this species.

The field biology of the platypus,Ornithorhynchus anatinus, was first studied by a number of expatriate biologists who visited the Australian colonies to collect specimens in the 1800s. Their work was followed in the early to mid–1900s by a group of resident natural historians and later by an increasing number of academic biologists. All of these workers contributed significantly to the current understanding of the field biology of this unique Australian species. The platypus occupies much the same general distribution as it did prior to European occupation of Australia, except for its loss from the state of South Australia. However, local changes and fragmentation of distribution due to human modification of its habitat are documented. The species currently inhabits eastern Australia from around Cooktown in the north to Tasmania in the south. Although not found in the west–flowing rivers of northern Queensland, it inhabits the upper reaches of rivers flowing to the west and north of the dividing ranges in the south of the state and in New South Wales and Victoria. Its current and historical abundance, however, is less well known and it has probably declined in numbers, although still being considered as common over most of its current range. The species was extensively hunted for its fur until around this turn of this century. The platypus is mostly nocturnal in its foraging activities, being predominantly an opportunistic carnivore of benthic invertebrates. The species is homeothermic, maintaining its low body temperature (32°C), even while foraging for hours in water below 5°C. Its major habitat requirements include both riverine and riparian features which maintain a supply of benthic prey species and consolidated banks into which resting and nesting burrows can be excavated. The species exhibits a single breeding season, with mating occurring in late winter or spring and young first emerging into the water after 3—4 months of nurture by the lactating females in the nesting burrows. Natural history observations, mark and recapture studies and preliminary investigations of population genetics indicate the possibility of resident and transient members of populations and suggest a polygynous mating system. Recent field studies have largely confirmed and extended the work of the early biologists and natural historians.

Blood samples were collected from the bill sinus of nine free-living platypuses (Ornithorhynchus anatinus) within 12 min of capture of each and again after 1 to 12 hr, New South Wales, Australia, 1981 to 1988. In seven animals which were not anesthetized, there was a significant (P < 0.01) fall in lymphocyte count between the two samples. The reduction ranged from 10 to 58% of the initial lymphocyte count and caused a significant reduction in the total white cell count (P < 0.05). Both the neutrophil and the lymphocyte counts increased in two platypuses which were anesthetized with ether prior to collection of the second blood sample. We propose that the peripheral blood lymphocyte count is a simple means of monitoring the stress response of non-anesthetized, newly-captured platypuses and may be a useful adjunct to behavioral observation.

The unique Australian monotreme, the platypus (Ornithorhynchus anatinus) potentially exerts a strong top-down influence on riverine food webs in eastern Australia. However, despite considerable interest in the evolutionary history and physiology of the platypus, little is known of its trophic relationships. To address this lack of knowledge we used stable isotope analysis, in combination with the analysis of food items stored in cheek pouches, to determine its position in a typical riverine food web. This was the essential first step in the process of designing a larger study to investigate the relative importance of top-down and bottom-up effects in rivers where the platypus occurs. We found that platypuses were feeding on a wide range of benthic invertebrates, particularly insect larvae. The similarity of δ13C and δ15N values recorded for the platypus, a native fish (Galaxias sp.) and the exotic mosquitofish (Gambusia holbrooki) indicated dietary overlap and potential competition for the same resources. Although cheek pouch studies identify most of the major groups of prey organisms, the potential for contribution of the soft-bodied organisms such as larval dipterans, is suggested by stable isotope analysis, indicating that the use of both techniques will be important in future ecological investigations.

The use of small mesh size gill and drum nets in the inland fishery until around 1950 probably had a considerable impact on platypus populations in most New South Wales rivers. The prohibition of nets in the capture of introduced salmonid species by the Fisheries Act, 1902 and the current fishing regulations have provided a good deal of protection to the species in most water bodies of the State. However, it is probable that the present overlap of commercial (and illegal) fishing operations with the distribution of platypuses in the lower Murray and Murrumbidgee rivers, and their affluent streams, are suppressing platypus numbers. An experiment indicated that the legal drum nets used in the industry are less of a threat to platypuses than the use of gill nets and the illegal nets used by poachers. Banning of gill nets from the industry and stringent law enforcement would largely protect platypus populations in the inland rivers. The current regulations of the eel fishery in New South Wales should minimize...

The platypus (Ornithorhynchus anatinus) feeds almost exclusively on benthic macroinvertebrates, yet no attempt has been made to link its energy demands with the productivity of its benthic macroinvertebrate prey. In the upper Shoalhaven River, New South Wales, we estimated macroinvertebrate production (in 2009 and 2011) from benthic samples and recorded platypus diet (2009 only) from cheek pouch samples. Ephemeroptera, Trichoptera and Chironomidae were the most numerous of six major groups in both the cheek pouches and the benthic samples. Three other groups (Odonata, Coleoptera, Sphaeriidae) were much less abundant in the benthos, but Odonata were common in the cheek pouches. In both years the Ephemeroptera, Trichoptera and Chironomidae had levels of production that were an order of magnitude higher than those of the three other groups. Rank correlation indicated that the most productive taxa were those most likely to occur in the cheek pouches. Total macroinvertebrate production for the six groups varied from 7.8gDWm–2year–1 in 2009 to 13.1gDWm–2year–1 in 2011. Previous estimates of field metabolic demand of the platypus enabled calculation of the number that could be supported by a given level of production. The observed levels of production were sufficient to support 13–27 platypuses in 2009 and 22–45 in 2011 along a 1.5-km reach of the river. Despite considerable landscape change, productive foraging habitat persists in the upper Shoalhaven River.

Non-invasive techniques for age assessment of wild mammals are needed for effective species management as well as research. In the case of the platypus, we investigated how morphology of calcaneal spurs and associated features in males and vestigial spur sheaths in females varies with age. Total spur length in males (spur tip to base of subtending epidermal collar) is greatest at 19–24 months and falls thereafter, with significant linear relationships evident between spur length and age of subadults (13–24 months old) and adults (≥25 months old). However, collar length/total spur length discriminates better between subadults and older animals than either collar length or total spur length alone. Juveniles can be reliably identified up to the age of 12 months (males) and 9 months (females) by the presence, respectively, of a sheath encasing the spur or a rudimentary spur sheath. A small proportion of young subadults (males, 4%; females, ≤2%) will be misclassified as juveniles due to sheaths being retained for longer than normal. Studies that need to identify juveniles very accurately as an age class should avoid sampling populations from August–October on the south-eastern Australian mainland (or May–October if subadult males also need to be identified correctly).

The platypus (Ornithorhynchus anatinus) has a wide distribution in Australia, encompassing the southern island of Tasmania and a broad latitudinal range of the mainland from the temperate south to the tropical north. We used 12 microsatellite markers from 235 individuals sampled from 13 river systems to examine patterns of genetic differentiation and gene flow throughout the species’ range. Using a Bayesian approach we identified three large-scale groupings that correspond closely to geographically distinct regions of the species’ distribution: the tropical northern mainland, the subtropical and temperate southern mainland, and Tasmania. Six additional clusters were found within the regional groups, three in the northern, two in the southern mainland regions, and the last in Tasmania. These clusters coincided with major river drainages. Genetic differentiation was generally high, with pairwise Fst values ranging from 0.065 to 0.368 for regions and 0.037 to 0.479 for clusters. We found no evidence of contemporary gene flow among the three clusters in the north, but some migration may occur between the larger clusters in the south. Due to the high genetic structuring and lack of gene flow between these three regional populations of the platypus we recommend their treatment as evolutionarily significant units (ESUs) within the platypus species. We have also detailed several smaller management units (MUs) existing within our study area based on subregional clusters and geographically significant features.

Population genetics is a powerful tool to increase the understanding of animals that may otherwise be difficult to study, such as the platypus (Ornithorhynchus anatinus). Focusing on two adjacent river systems in New South Wales, we used 12 polymorphic microsatellite loci to investigate the population dynamics of the platypus. We found that individual river systems acted as discrete population units. Evidence of migration, presumably overland, between systems explains how these units remain connected. This establishes an isolation-by-distance pattern that maintains species continuity across most of the mainland distribution. This improved understanding of population structure will be a valuable contribution to designing accurate management plans for the long-term conservation of this unique Australian animal.

During his 15 month sojourn in Tasmania, Monsieur Jules Verreaux devoted most of his efforts to studying the platypus, including making observations in the field. While some of his observations were accurate and original, others were at odds with those of later naturalists and current scientific findings. Like most other 19th century expatriate naturalists from the Northern Hemisphere, Verreaux failed to determine that the species laid eggs but he described some intriguing attributes which remain controversial and/or unsubstantiated by the work of more recent naturalists and scientists. Perhaps the most controversial was that the newly emerged young prod the mammary areas of the female and take the exuded milk from the surface of the water. An annotated summary of Verreaux's findings is presented, along with the full text of his work in French and a translation of this text into modern English.

Data from the New South Wales Rivers Survey on the occurrence of platypuses have provided the most recent and comprehensive record of platypus distribution in the State. The species was most commonly reported from the montane and coastal regions, being less common on the western slopes and uncommon in the rivers of the western lowlands. The observations confirmed those from earlier community-based surveys. In contrast to the distribution of native fish species, there appears to have been little change in the overall state-wide distribution of the platypus in response to degrading processes in the rivers of New South Wales, although nothing is known of the stability of their population numbers.

To investigate the genetic relationships within and between platypus populations, molecular genetic methods employing DNA analysis are very effective, and microsatellite variation has been shown to be the most effective for population studies. Microsatellites are segments of DNA with tandem repeats of short sequence motifs, usually 1-6 base pairs of nucleotides, and they are highly variable and easy to score. Several microsatellite loci have been detected and sequenced, and PCR primers have been constructed and used to identify several polymorphic microsatellite variants. In the main breeding population, from which we have a collection of over 80 animals, two alleles not found among resident or other captured males were detected amongst juveniles. From our combination of microsatellite and mtDNA analysis, these alleles are likely to be derived from uncaptured transient males which participated in breeding. We therefore suggest that the mating system in this population of platypus involves polygyny and sneaking. Allele frequency differences have been detected between sub-populations within the same stream, consistent with observations on mtDNA genotypes. As well, there are allele frequency differences between populations from different streams and these show continuous geographical gradation, consistent with an isolation-by-distance geographical structure.

In the summer of 1990-91 the first captive breeding of platypus (Omithorhynchus anatinus) in 47 years, and only the second ever, occurred in a small resident population at Warrawong Sanctuary, South Australia. DNA fingerprinting and analyses employing the maternally inherited mitochondrial genome have been used to determine family relationships within this population Using hypervariable DNA sequences cloned from other species to probe blots of DNA from the Warrawong platypuses, individual-specific banding patterns have been observed that allow the identification of family relationships within the population. A novel method for detecting maternal relationships within platypus populations, based on polymerase chain reaction analyses of the highly polymorphic mitochondrial control region, is also presented.

Using implanted radiotransmitters, we monitored body temperatures in five platypuses ranging freely in the Thredbo River in Australia's southern alps between April and October 1988, where the water gets as cold as any that a platypus is likely to encounter. Activity pattern showed a distinct daily cycle. No evidence of hibernation or even brief periods of torpor was found, all individuals maintaining body temperatures close to 32-degrees-C throughout the winter (mean+/-s.d., 32.08 +/- 0.75-degrees-C, range 29.2-34.6-degrees-C, n = 2237). No differences were found between the means or the variances of body temperatures of animals during day-time rest in stream-bank burrows and those during night-time foraging in winter at temperatures as low as 1.0-degrees-C.

Platypuses captured in various water bodies in New South Wales were weighed and measured. There was considerable variation in both weights and lengths of animals measured from the different localities, with those from the Murrumbidgee River being larger than those from any other area. Mean lengths of adult males ranged between 53.3 ± 4.0 cm for individuals from Childowla on the Murrumbidgee River to 46.4 ± 0.5 cm for individuals from the Barnard River, while adult female mean lengths ranged between 47.6 ± 0.4 cm to 40.1 ± 0.2 cm for animals from the same localities. In some areas there was significant variation in weights with seasons, with either males or females losing weight in winter and gaining it during the following summer and early autumn. The highest mean weights for both males and females were again those for animals from Childowla (in February), being 2115 ± 95.7 g and 1398 ± 34.8 g respectively. Juvenile Platypuses emerged from nesting burrows around February in the Shoalhaven River at 81-88% of adult length, and 56-67% of adult weight for that month. After an initial spurt between February and April, growth was retarded in these animals during winter. Juvenile females grew rapidly during their first spring and reached adult size by the following January. Juvenile males also grew during this period but did not reach full adult size by this month. They were still recognisable as subadults using spur morphology. Possible reasons for the observed differences in size between areas are discussed.

Although platypus spend short periods feeding in captivity, they do spend up to several hours at a time foraging for food in the wild. The $T_{b}$ of platypus netted during feeding periods in the water in various areas of New South Wales varied from a mean value of 32.1 C in the summer to 30.4 C in the winter. Struggling and the destruction of the fur insulation are thought to account for these temperatures being lower than those recorded in captive animals, especially in winter. The $T_{b}$ of the platypus in air over a temperature range of 5-30 C is between 32 and 33 C. Platypus which were confined to water or allowed to enter or leave it at will maintained $T_{b}$ of between 33 and 34 C. The slight elevation of $T_{b}$ from resting levels in air is attributed to muscular activity and the restriction of heat loss by changes in tissue insulation.

Feeding in the platypus Ornithorhynchus anatinus was investigated by identifying material found in the cheek pouches of animals trapped in nets in a study area on the upper Shoalhaven River, N.S.W. Benthic samples were taken in the rapids and pools of the river and the relative abundance of food items available was related to the food found in the platypus cheek pouches. The main food organisms found were insect larvae, notably Trichoptera, Diptera, Coleoptera, Ephemeroptera and Odonata. Subsidiary food items found included freshwater shrimp Paratya australiensis, bivalve mollusks (Sphaerium sp.) and one anuran. The main food items were generally taken in direct proportion to their numerical abundance in the river. Comparisons are made with the food selected by the brown trout Salmotrutta from the area. Estimates are made of the weights of invertebrate food necessary to maintain a platypus in various seasonal conditions.

The effects of industrial pollution were determined by comparing the pattern of development of marine fouling communities situated along a pollution gradient within Port Kembla Harbour (Australia) with those from nearby Wollongong Harbour, a relatively unpolluted area. Fifty-three fouling species were found in the communities from Wollongong Harbour compared to only 40 in those from Port Kembla Harbour. Twenty-eight species (including many bryozoans) occurred only in the former, while 15 species occurred solely in the latter. Ten of the 25 species common to both areas were more numerous in Port Kembla Harbour, probably because of the greater availability of free substratum and food in this area. The species richness of fouling communities in Port Kembla Harbour was found to decrease as pollutant concentrations increased. In both study areas, communities established in summer showed significantly higher species richness than those whose development was initiated in winter. This difference was less pronounced in Port Kembla Harbour and was attributed to the effects of pollution on larval settlement. Although species richness increased at all sites through time, Wollongong Harbour communities contained a greater number of species at the end of the experiment than communities from Port Kembla Harbour. Despite this, fewer species were found in the very early developmental stages of the communities from Wollongong Harbour. This result highlights the inherent problems associated with using species richness or diversity measures as a means of determining marine environmental quality.

The platypus, Ornithorhynchus anatinus had a minimum resting metabolism in air of 2.2 W·kg−0.75 at a $T_{a}$ of 25 C. In absolute terms, this metabolism was 8% less than that of marsupials in general, and 35% lower than that of eutherian mammals. The increase in metabolism in response to cold in air was 1.8 times the resting level at a $T_{a}$ of 5 C. However, the immersion in cold water raised this to 3.2 times the resting metabolism (7.0 W·kg−0.75 at a water temperature of 5 C). The resting metabolism of the platypus was approximately 32% higher than that of its terrestrial monotreme relative, the echidna (Tachyglossus aculeatus). Evaporative heat loss (EHL) by the platypus was low, being 0.62 to 1.36 W·kg⁻¹ over a temperature range from 5 to 30 C. The maximum measured water loss at 30 C (probably due to sweating), although lower than the level considered to constitute thermal sweating in large mammals, possibly plays a significant part in cooling the platypus during moderate heat stress and exercise. A...

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Platypus milk fat contains 98.5% triglyceride. Polyunsaturates (C18∶2-C22∶5) account for 29% of the triglyceride fatty acids in the milk fat and 32% of the total fatty acids in the lipid of the food of the platypus. Linoleate and arachidonate are the major ω6 polyunsaturates of both food and milk lipids. However, while the ω3 polyunsaturates linolenate and eicosapentaenoate are present in both food and milk, docosapentaenoate is present in meaningful amounts in milk only. It is suggested that with the exception of 22∶5ω3, the polyunsaturates in platypus milk originate in the diet.

Although much is known about the biology of monotremes, many important aspects of their reproduction remain unclear. Studies over the last century have provided valuable information on various aspects of monotreme reproduction including the structure and function of their reproductive system, breeding behaviour, sex determination and seasonality. All three living genera of monotremes have been successfully maintained in captivity, often for long periods, yet breeding has been rare and unpredictable. When breeding has occurred, however, significant gains in knowledge have ensued; for example a more accurate estimate of the gestation period of the platypus and the incubation period for the Tachyglossus egg. One of the great challenges for zoos has been to understand why breeding of monotremes is difficult to achieve. Analysis of breeding successes of platypuses and short-beaked echidnas provides some insights. The evidence suggests that although annual breeding seasons are regionally predictable, individual adult females breed unpredictably, with some showing breeding intervals of many years. The reason for this variation in individual breeding intervals may be resource-dependant, influenced by social factors or may even be genetically induced. Better knowledge of factors that influence breeding intervals may improve the success of monotreme captive breeding programmes. More certainty in captive breeding is also an important issue for enterprises wishing to trade in Australian wildlife since current legislation limits export of Australian fauna for display to at least second-generation captive-bred individuals. Given their unique evolutionary position, knowledge of reproduction in monotremes needs to be gained in advance of any future population declines so that appropriate strategies can be developed to ensure their survival.

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The standard metabolic rates (SMR) of species from all extant monotreme genera were determined together with body temperatures. The echidnas, Zaglossus bruijni and Tachyglossus aculeatus, of the Family Tachyglossidae, both had an SMR 25-30% of predicted eutherian levels. The platypus Ornithorhynchus anatinus, however, had a much higher SMR. The weight-independent values (watts, kg*-075) were 0.86, 0.98 and 2.21 respectively for Z. bruijni, T. aculeatus and 0. anatinus. Body temperatures were similar, however, with means in the range 31.3-32�C. The data are suggested to support the idea of a gradual evolution in metabolic capability rather than marked jumps in metabolic levels.