Good news for Coliban Platypus population
Posted on 3 December, 2020 by Frances
A platypus survey recently conducted by the Australian Platypus Conservancy (APC), in partnership with Malmsbury Landcare Group, succeeded in capturing 8 animals (6 males, 2 females) in a 3-kilometre segment of the Coliban River in and near Malmsbury township in central Victoria. APC’s latest newsletter provided the following update on their work.
The survey’s main objective was to replicate APC surveys previously carried out in 2001 (near the start of the millennium drought, when 10 animals were recorded in the study area) and again in 2010 (shortly after the drought ended, when only two animals were recorded). Given that only a fraction of the animals found in an area is expected to enter nets on any given night, the recent results are consistent with platypus abundance having now recovered to pre-drought levels.
This is not particularly surprising given that a female platypus matures at the age of two years and average fertility in reasonably productive habitats is 1.9 babies per litter. The low number of females encountered in the most recent survey probably reflects the fact that it was carried out in October, when many breeding females will be spending a lot of their time in a nesting burrow – either incubating eggs or caring for recently hatched young.
Both the 2001 and 2020 surveys found:
- At least one platypus was captured at every site where nets were set.
- Two males and two females were recorded at Malmsbury township.
- There was evidence that a healthy rakali population coexists with platypus in the study area.
Viewed at the catchment scale, the Malmsbury platypus sub-population is part of a much larger group of animals occupying around 50 kilometres of river channel between Malmsbury Reservoir and Lake Eppalock. Although not all of this area will necessarily be characterised by platypus densities that are as high as those at Malmsbury, recent eDNA evidence indicates that animals occur widely, with the pattern of recent platypus sightings also helping to confirm that this part of the Coliban system holds a regionally important platypus population that should be managed with care to ensure its long-term survival.
Considered at a more local scale, the substantial pools located in Malmsbury township are likely to support successful platypus reproduction in both wet and dry years, with two females captured there in both 2001 and 2020. The high quality of this habitat reflects not only the pools’ size but also the provision of reliable outflows from Malmsbury Reservoir and many years of hard work by Malmsbury Landcare members to protect and improve adjoining riparian vegetation.