Tracking the Swamp Wallaby
Fiona Haddock

Wallaby underpass on the F3 freeway

For some time, the national parks authorities believed there was a gratifying absence of road-kill on the F3 freeway. But with further investigation, the reality became clear. In fact, the Roads and Traffic Authority (RTA) was carefully cleaning up the deceased animals each day.

The swamp wallaby project, sponsored by the Foundation, was motivated by the number of animals being killed on the freeway. Carried out by the University of New South Wales (UNSW) Road Ecology Research Group, the study aimed to better understand the impact of the F3 on neighbouring wallabies.

It looked at how they went about their daily routines and whether they were in a poorer condition as a result of where they lived.

Getting started

For the purposes of the study, the researchers radio-tagged wallabies within two designated areas. One was in Brisbane Waters National Park 60 km north of Sydney. It involved a section between the F3 and the old Pacific Highway and included an 80 metre underpass. For the second area the researchers chose the nearby Muogamarra Nature Reserve. It is also bordered by the F3 and Ku-ring-gai Chase National Park. There is no underpass in this area.

Sand traps placed in the underpass captured the tracks of a solitary female Above Photos: UNSW Road Ecology Research Group

The number of wallabies discovered was surprisingly few, only nine in total. “We did some intense capture of wallabies every week within coo-ee of the road,” explains Dr Daniel Ramp, research fellow at UNSW and project manager. “However we didn’t catch as many as we thought we would.”

The group then weighed and measured the wallabies and put radio-collars on them, tracking them night and day for three months. The findings were often surprising.

Cramped quarters

Despite the small number of wallabies present, the researchers concluded that these animals were living in very close proximity to each other. Previous studies have shown swamp wallabies to be quite solitary. However, here the home range of each wallaby, being the area in which they tend to roam, overlaps by about 80% with other animals in the group. “The animals are living on top of each other,” says Dr Ramp.

The animals also chose a smaller home range. In a 2005 study the wallabies used a 76 hectare range on average. Here this area was significantly less at about 11 hectares on average.

It also became clear that, with the exception of one wallaby, the group wasn’t crossing the road. “Those living in proximity of the road were aware of the road and using it as a boundary,” says Dr Ramp.

The Swamp Wallaby or Black Wallaby or 'Stinker' is the only member of the genus Wallabia, set apart from other wallabies by its unique combination of genetic, dental, reproductive and behavioural characteristics. Mainly feeding on ferns, shrubs and bushes this common marsupial prefers its solitude. Swamp wallaby (Wallabia bicolor) Max Herford

However, there was one who wanted to get to the other side, a female wallaby. The research group set up a sand trap in the underpass to monitor the tracks of wildlife passing through. Despite the presence of numerous wallaby prints it was discovered they only came from the one female. There was no sign any of the other wallabies in the vicinity used the underpass at all.

Another curious discovery relates to the health of the wallabies. The study indicates the wallabies living near the freeway are much fitter than the core wallabies. This is based on the fact they are heavier compared to their foot length. “It’s a bit counter-intuitive,” agrees Dr Ramp. One of the reasons could be because of good quality habitat at the roadside. This would also explain the strong overlap between wallabies, there is enough food for several wallabies within the area.

Another path

Clearly, there are many more questions that have still to be answered. To this end, the group hopes to reach an agreement with the RTA to monitor the road-kill on the freeway and to provide DNA samples for genetic analysis.

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