Wildlife and endangered species management
Keeping tabs on a marathon swimmer: monitoring migration patterns of the Australian platypus

(excerpted from: Australian Platypus Conservancy, Ripples, Issue 13, Summer, 1999Scientia-platypus-swimming)

When Australian Platypus Conservancy researchers captured a young male platypus last October during the first platypus survey work to be undertaken along Steels Creek (in Melbournes’s outer eastern suburbs near Yarra Glen), it seemed reasonable to assume they had encountered a “new” animal. To their astonishment, when they dutifully checked the young male for the presence of a TROVAN identification transponder, the scanner gave a beep of recognition and flashed an ID code on the display screen. A quick search of the APC database revealed the origin of the mystery platypus: he had been caught as a juvenile some 18 months earlier in Andersons Creek near the town of Warrandyte, about 40 kilometers away as the platypus swims!

It’s always interesting to catch up with an old acquaintance. In this case, researchers were very pleased to note that the male had grown substantially in the interim, gaining 340 grams (about 25% of his initial body weight) and measuring nearly 8 centimeters longer than when he was first handled. The discovery of this marathon swimmer also has some important implications for platypus research and management. In the first place, the distance moved by the Steels Creek male is much greater than the previous platypus travel record of around 15 kilometers (set by an adult male in the months prior to the breeding season). Clearly, much remains to be learnt about platypus movement patterns, especially those of juveniles. In turn, this information is needed to understand (and predict) the extent to which platypus populations can survive drastic changes to waterways over time. Secondly, the re-capture of an animal so far from its original location demonstrates the value of wide-scale survey and monitoring work for platypus.

Now in its fifth season, the Urban Platypus Program has seen the APC undertake mark-and-release studies in co-operation with Melbourne Water along many hundreds of kilometers of waterways in the metropolitan region. Animals were individually identified with TROVAN microchip transponders, making it possible to learn a great deal about platypus population turnover and individual survival, as well as recognizing long distance movements. Lastly, it is important that the most appropriate scale or unit of management for these animals is an entire river catchment. In the case of the Steels Creek platypus, the main surprise for researchers was not so much that he had travelled dozens of kilometers but that the movement had actually been documented by humans. Studies in the Yarra River catchment and elsewhere have shown that platypus commonly occupy home ranges stretching up to 7 kilometers in length - and may patrol all of that area in a single night. As well, animals regularly include parts of more than one waterway in a given home range, for example, a section of a creek along with an adjoining segment of river. Thus, while it should never be considered a waste of time to preserve or improve a small stretch of stream, the long-term survival of platypus populations ultimately depends on maintaining very large networks of healthy waterways - and working co-operatively across individual properties and government boundaries to achieve that end.