Habitat use by platypus (Ornithorhynchus anatinus) in a modified Australian Wet Tropics catchment, north-eastern Queensland

Abstract

The habitat affiliations of platypus (Ornithorhynchus anatinus) were investigated in the upper Barron River and its tributaries, a modified Wet Tropics catchment in north-eastern Queensland, Australia. A habitat assessment was carried out at 46 sites, and a visual monitoring survey was used to determine whether platypus were present at these sites. Habitat assessment of riparian and in-stream parameters included an evaluation of factors known to influence platypus populations: disturbance level, stream depth and width, riparian continuity, the amount of overhanging vegetation, bare soil along banks, large woody debris, weeds, pool and riffle area and substrate types. Sites where platypus sightings occurred were characterised by a minimum channel width of 3.8 m and slow-flowing pools with depths of 0.49–2.0 m. These findings concur with platypus habitat preferences as described in other regions, although some in-stream and riparian factors considered as important components of platypus habitat in other studies (riparian continuity, large woody debris, undercut banks and coarse stream substrate) were not associated with the presence of platypus in this study. This study represents the first investigation of the influence of human-induced habitat modification on platypus affiliations in an Australian Wet Tropics river system.

The platypus: evolutionary history, biology, and an uncertain future

“…Home ranges vary spatially and temporally with breeding season, age, and sex (Grant et al 1992; McLeod 1993; Serena 1994; Gust and Handasyde 1995; Serena et al 1998; Otley et al 2000; Serena and Williams 2012a; Bino et al 2018). Preferred habitat tends to include consolidated earth banks with large trees in the riparian zone, vegetation overhanging the stream channel, wide streams with in-stream organic matter, shallow pools, coarse woody debris, and coarse channel substrates, but platypuses still occur in habitats without some of these features, often in quite degraded agricultural settings (Rohweder 1992; Bryant 1993; Ellem et al 1998; Serena et al 2001; Milione and Harding 2009). In a Tasmanian study (Lunn 2015), catchment-scale factors (e.g., nearest large stream, catchment area) were found to be more useful indicators of platypus presence in high-order streams, whereas “finer-scale” local habitat variables (e.g., substrate, in-stream barriers) were particularly important indicators of stream use by platypuses in small headwater streams.…”

“…However, relatively little is known about the species’ past and present distribution and numbers, limiting accurate evaluation of its conservation status and future population trajectories. Recent documented local declines and extinctions identify that the species is facing considerable threats in some areas (Lintermans 1998; Lunney et al 1998; Serena et al 1998; Rohweder and Baverstock 1999; Otley 2001; Milione and Harding 2009). However, estimates of population sizes are particularly difficult to obtain, given low recapture rates and the substantial effort required (Grant 2004a; Serena and Williams 2012a).…”