Distribution and characteristics of the platypus (Ornithorhynchus anatinus) in the Murrumbidgee catchment

Abstract

Little is known of the current status of platypus (Ornithorhynchus anatinus) populations in the Murrumbidgee catchment and other west-flowing rivers in the Murray–Darling Basin. Platypus distribution in the Murrumbidgee catchment was determined from sightings, reports by government departments, the literature and a capture–release study. The platypus was found to be widespread in the catchment, including all subcatchment and elevation categories, but most reports were from the middle and upper subcatchments. Sixty-five captures of 55 individual platypuses were made during 61 trap-nights to 31 study sites in the Murrumbidgee catchment during 2009–10. Only three juveniles (all females) were captured and recapture rates were low, with only nine platypuses captured more than once. Adult males had body weights of 980–2180 g and body lengths of 42–60 cm (n = 32). Adult females weighed 795–1480 g and were 38–52 cm long (n = 20). Tail fat index was significantly affected by season and platypus age, while in comparison, season, platypus length and weight had a significant effect on tail volume index. This study established a baseline that provides a starting point from which the impacts of environmental disturbances or diseases occurring over time can be measured and investigated.

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.…”

“…Mucormycosis has been reported in certain river catchments in Tasmania but, despite the presence of M. amphibiorum in amphibians and the environment, the disease has never been reported in mainland states (Spear et al 1994;Stewart and Munday 2005). Clinical signs of mucormycosis vary from nonulcerated, hairless nodules (,10 mm diameter) or plaques (10-54 mm diameter) (Connolly and Obendorf 1998;Connolly et al 2001) to cutaneous ulcers (5-100 mm diameter) (Munday et al 1998;Connolly et al 2001). These ulcers can progress to involve underlying muscle up to 10 mm below the skin, and lesions are sometimes found in the internal organs, particularly the lungs (Munday et al 1998;Connolly et al 2001;Stewart and Munday 2005).…”

“…A range of issues relating to individual platypus health has been addressed by previous studies. Platypus body mass, body size, and body condition have commonly been reported (Grant and Temple-Smith 1983;Serena and Williams 1997;Connolly and Obendorf 1998). Reference ranges for hematology and biochemistry parameters have been produced (Whittington and Grant 1984;Booth and Connolly 2008;Geraghty et al 2011).…”

“…These ulcers can progress to involve underlying muscle up to 10 mm below the skin, and lesions are sometimes found in the internal organs, particularly the lungs (Munday et al 1998;Connolly et al 2001;Stewart and Munday 2005). The ulcers are assumed to lead to impaired thermoregulation (due to loss of fur) and impaired mobility (Connolly and Obendorf 1998) and are likely to predispose affected animals to secondary infections and flystrike (Connolly and Obendorf 1998;Munday et al 1998). Mucormycosis can be fatal and is considered a conservation threat (Munday et al 1998).…”