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Furlan E.,University of Melbourne | Griffiths J.,CESAR Consultants | Griffiths J.,Australian Department of Primary Industries and Fisheries | Gust N.,Australian Department of Primary Industries and Fisheries | And 6 more authors.
Australian Journal of Zoology | Year: 2011

The body size of the platypus (Ornithorhynchus anatinus) is known to vary across both its latitudinal range and relatively short geographic distances. Here we consider how variation in platypus length and weight associates with environmental variables throughout the species' range. Based on data from over 800 individuals, a Bergmann's cline (increased body size in regions of lower temperature) was detected across the species latitudinal range. The opposite association, however, was present at smaller scales when comparing platypus body size and temperature within southern mainland Australia, or within an individual river basin. Temperature regimes alone clearly did not dictate body size in platypuses, although disentangling the effects of different climatic variables on body size variation was difficult because of correlations amongst variables. Nevertheless, within suitable platypus habitat in south-eastern Australia, areas of relatively lower rainfall and higher temperatures were typically associated with larger-bodied platypuses. The potential benefits to larger-bodied animals living under these conditions are explored, including consideration of variation in energy expenditure and food availability. Assuming these associations with environmental variables are biologically significant, a shift in platypus body size is anticipated in the future with predicted changes in climate. © 2011 CSIRO.

Martin E.H.,University of Melbourne | Walsh C.J.,University of Melbourne | Serena M.,Australian Platypus Conservancy | Webb J.A.,University of Melbourne
Austral Ecology | Year: 2014

The platypus (Ornithorhynchus anatinus), like many other stream-dependent species, is reportedly sensitive to catchment urbanization. However, the primary mechanism limiting its distribution in urban environments has not been identified. We created species distribution models for three platypus demographic classes: adult females (which are exclusively responsible for raising young), adult males (which are more mobile than females), and first-year juveniles. Using live-trapping data collected in Melbourne, Australia, we tested whether distributions of the three demographic classes were better predicted by catchment urban density (total imperviousness), by urban stormwater runoff (catchment attenuated imperviousness), or by stream size (catchment area). Two variants of each predictor variable were developed, one that accounted for platypus mobility, and one that did not. Female distribution was most plausibly predicted by stormwater runoff (accounting for mobility), with a steep decline in reporting rate from 0 to 10% attenuated imperviousness. Male distribution was equally plausibly predicted by stormwater runoff and urban density (both accounting for mobility), with a less steep and more uncertain decline with imperviousness than females. Juvenile distribution was most plausibly predicted by stream size (accounting for mobility), but both stormwater runoff and urban density (accounting for mobility) were nearly equally plausible predictors. The superior performance of models that accounted for mobility underscores the importance of accounting for this in species distribution models of highly mobile species. Platypus populations in urban areas are likely to be affected adversely by urban stormwater runoff conveyed by conventional drainage systems, with adult females more limited by runoff-related impacts than adult males or juveniles. Urban platypus conservation efforts have generally focused on restoring riparian and in-stream habitats on a local scale. This is unlikely to protect platypus from adverse impacts of urban stormwater runoff, which is most effectively managed at the catchment scale. © 2013 Ecological Society of Australia.

Serena M.,Australian Platypus Conservancy | Williams G.A.,Australian Platypus Conservancy | Weeks A.R.,University of Melbourne | Griffiths J.,293 Royal Parade
Australian Journal of Zoology | Year: 2014

An understanding of animal population dynamics relies on identifying life-history attributes associated with population growth and determining how these are affected by environmental variables. We analysed platypus population processes over a 10-year period through mark-recapture studies conducted in three spatially independent stream systems located in the suburbs of Melbourne, Australia. The three populations were collectively characterised by a slightly male-biased adult sex ratio (1.15:1) and relatively low reproductive success (<0.5 juvenile captured annually per adult female). An estimated 16% of core residents disappeared annually and 18% of marked juveniles were recaptured as adults. However, some demographic parameters (reproductive success, frequency of non-core adult captures) varied significantly among populations. Estimates of annual core population size in the three systems varied asynchronously, with different trajectories in population size potentially reflecting habitat differences (amount of urban development, reliability of surface flow) as well as variation in spatial isolation and catchment history (implementation of stream rehabilitation programs, occurrence of severe floods). Across all three populations, significant variability in annual reproductive success was explained by linear relationships with the amount of rainfall recorded in the five months before breeding (positive) and after juveniles emerge from nesting burrows (negative). © CSIRO 2014.

Serena M.,Australian Platypus Conservancy | Grant T.R.,University of New South Wales | Williams G.A.,Australian Platypus Conservancy
Fisheries Research | Year: 2016

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. © 2015 Elsevier B.V.

Williams G.A.,Australian Platypus Conservancy | Serena M.,Australian Platypus Conservancy | Grant T.R.,University of New South Wales
Australian Mammalogy | Year: 2013

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). © Australian Mammal Society 2013.

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