Spatial organisation and movements
Based on radio-tracking studies, the home ranges of neighbouring female platypus occupying creeks in the Yarra River catchment near Melbourne often overlap by about half their total length. Adult males occupy areas which are not necessarily shared with other males but typically overlap the home ranges of two or more adult females. In cases where male home ranges do overlap, the males appear to try to avoid each other when active.
The home ranges of adult males tracked for a few weeks in these creek habitats typically include 1-7 kilometres of channel, as compared to 1-4 kilometres for adult females. Males and females both visit roughly one-quarter to three-quarters of their total home range in most foraging periods. However, an adult male has been recorded to travel up to 10.4 kilometres (including backtracking) in a single overnight period, whereas the longest corresponding distance for an adult female is 4.0 kilometres.
Along the Goulburn River (where it presumably is much harder for an adult male to exclude other males from a given area, due to the greater width and depth of the channel), male home ranges overlap throughout the year, but less overlap is apparent during the breeding season than at other times of year.
Male home ranges have been found to vary in length from 0.55-2.8 kilometres, corresponding to 2.45-15.45 hectares of foraging area. However, animals do not utilise all parts of their home range equally, with an intensively used core area typically comprising 30% of the total home range area. Including backtracking, animals were recorded to travel up to 4.1 kilometres in a given night.
Longer movements by platypus have been documented, including a radio-tagged adult male that travelled more than 15 kilometres (between two creeks in the Yarra River catchment) on at least two occasions within a period of 10 weeks. Based on mark-recapture studies, a young male is known to have moved about 40 kilometres in the Yarra system over a period of 18 months or less (from Andersons Creek to Steels Creek), and a young male travelled nearly 48 kilometres in the Wimmera River catchment over a period of 7 months or less (from the Wimmera River to Mount Cole Creek).
Due to their mobility, platypus may occasionally be seen in virtually any part of a river system where they occur. With respect to conservation management, this mobility has three important consequences:
- Suitable vacant habitats are predicted to be occupied quite promptly by platypus through natural colonisation (particularly if the new habitats are located reasonably close to areas already supporting the species).
- Stretches of river or stream which do not support a resident platypus population may still constitute important habitat for the species, by providing corridors along which breeding males and dispersing juveniles can travel.
- It is essential that manmade structures (weirs, flood fences, culverts, irrigation control gates, etc.) placed along natural water bodies or manmade channels that are accessible to platypus should be built in a manner which facilitates safe passage by the animals.
Gardner, J.L. and Serena, M. (1995). Spatial organisation and movement patterns of adult male platypus, Ornithorhynchus anatinus (Monotremata: Ornithorhynchidae). Australian Journal of Zoology 43: 91-103.
Gust, N. and Handasyde, K. (1995). Seasonal variation in the ranging behaviour of the platypus (Ornithorhynchus anatinus) on the Goulburn River, Victoria. Australian Journal of Zoology 43: 193-208.
Serena, M. (1994). Use of time and space by platypus (Ornithorhynchus anatinus: Monotremata) along a Victorian stream. Journal of Zoology (London) 232: 117-131.