The platypusOrnithorhynchus anatinusin headwater streams, and effects of pre-Code forest clearfelling, in the South Esk River catchment, Tasmania, Australia

Abstract

This study examined the occurrence, relative abundance and condition of platypuses in the upper catchment of the South Esk River, in north-east Tasmania, Australia, and the impact of past forestry activities on the occurrence of platypuses in first order headwater streams. The main trapping sites were in twenty first order streams, eight second-fourth order headwater streams and one fifth order stream reach. Additional trapping was also undertaken in the South Esk River and farm dams. Sites were trapped during late spring/mid summer and early autumn. A total of 78 individuals were caught in the study area. Platypuses were caught at all sites trapped in the second-fourth order and fifth order stream reaches and in nine of the twenty first order streams. Catch success was greatest in the fifth order stream reach and lowest in the first order streams. There was a trend toward a higher proportion of juvenile/subadult males in the lower order stream sites. For the higher stream orders, a higher proportion of individuals was caught during the summer, however for the first order streams, a higher proportion was caught during the autumn trapping period.Information collected on the body mass, body length and condition of individuals indicated smaller individuals with a higher tail fat index in the lower order streams.There was a trend toward a lower occurrence of platypuses in the first order streams, which had been disturbed 15 years previously by forestry operations compared to first order streams with relatively undisturbed catchments. Differences in occurrence of platypuses were related to differences in the 'instream' and riparian characteristics of disturbed streams compared to undisturbed streams. Headwater streams form a large proportion of a river system. Although they provide more marginal habitat for the platypus than larger river reaches, their disturbance may be an important land management issue in the conservation of this species, particularly in river catchments where the species is impacted by other environmental changes or disease.

Investigation Into Individual Health and Exposure to Infectious Agents of Platypuses (Ornithorhynchus Anatinus) in Two River Catchments in Northwest Tasmania

“…We found no evidence of mucormycosis in the study animals but found a new differential diagnosis for this disease. Platypuses are sexually dimorphic in body length and body mass and are generally larger in Tasmania (Grant and Temple-Smith 1983;Connolly and Obendorf 1998;Munks et al 1998;Bethge 2002;Koch et al 2006;Gust and Griffiths 2011). Our findings are consistent with these observations.…”

“…Our findings are consistent with these observations. Studies of Tasmanian platypuses have shown mean mass in different river systems in the ranges 0.91-1.65 kg and 1.47-2.5 kg for females and males, respectively (Connolly and Obendorf 1998;Stewart 2001;Bethge 2002;Koch et al 2006;Gust and Griffiths 2011). Mean body masses in our study were near the middle of these ranges and were very close to the mean values of 1.3 kg for females and 2.1 kg for males reported by Macgregor (2008) in the Inglis River Catchment.…”

Platypus (Ornithorhynchus anatinus) body size, condition and population structure in Tasmanian river catchments: variability and potential mucormycosis impacts

“…Platypuses exist in the majority (44 of 48) of Tasmanian river catchments (Gust and Griffiths 2010), where they occupy diverse freshwater habitats including rivers, streams and creeks, lakes, tarns and farm dams from sea level to an altitude of 1200 m (Rounsevell et al 1991). Differences in the mean size of adult platypuses have been described among some Tasmanian rivers and lakes (Koch et al 2006). However, it is currently unclear how variable Tasmanian platypus morphometrics and demographics are over their heterogeneous environment, or what the key spatial scales are for differences.…”

“…Even small differences in these conditions may be important, as Tasmanian platypuses are known to spend more than 12 hours a day foraging for prey (Bethge et al 2003;Bethge et al 2009). Initial evidence suggests platypuses using upper headwater streams in Tasmania may be smaller than those in lower catchment reaches (Koch et al 2006;Olsson Herrin 2009), and smaller individuals have been reported from smaller streams on the mainland (Handasyde et al 1992). The spatial scale of platypus breeding populations in Tasmania is currently unclear , although high levels of genetic differentiation among some Tasmanian river catchments (Furlan et al 2010) suggest catchments may be reasonable proxies for local platypus populations, and form sensible management units.…”

Evaluating the capacity of constructed wetlands to sustain a captive population of Platypus (Ornithorhynchus anatinus)

“…C o n s t r u c t e d p o n d s c a n provide a permanent water body, stable food supply and b a n k s f o r b u r r o w construction. In a similar study conducted in Tasmania by Koch et al (2006), two j u v e n i l e s w e r e f o u n d foraging in a constructed dam. This evidence appears to confirm that constructed d a m s , s u c h a s t h o s e a t Warrawong Sanctuary, can provide suitable areas for Platypus foraging, breeding and juvenile dispersal.…”