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Roadside wallabies appear to be streetwise

Rock Wallaby Sign

Rock wallaby that lived along the roadside were fatter for their age than wallabies that lived elsewhere (Source: Peter Firminger/Flickr)

Fat wallabies Countless kangaroos and wallabies end up as roadkill but individuals of at least one species are finding unexpected benefits living by the roadside, new research has found.

Swamp wallabies that make their home alongside the freeway to the north of Sydney seem to be better fed and less likely to be hit by road traffic than counterparts in a nearby nature reserve, says researcher, Dr Daniel Ramp, from the School of the Environment of the University of Technology, Sydney.

"For some species, like swamp wallabies these environments can be good," he says.

He and colleague Dr Dror Ben-Ami report their findings in a recent issue of Wildlife Research.

Kangaroos and wallabies have struggled to coexist with the development of towns and cities.

"If you look at the Sydney region, prior to settlement there were red-necked wallabies, eastern grey kangaroos, swamp wallabies and a number of smaller ones and pretty much they've all been lost except for the swamp wallaby," says Ramp.

He says one reason for this is that swamp wallabies are not fussy eaters, are solitary and keep a low profile.

But, still the animals are the favourite food of wild dogs and dingoes, and the second most killed animal on Sydney's roads after brushtail possums.

"Even though they are the last remaining survivors they are still being impacted severely and appear to be just hanging on," says Ramp.

Roadside study

As part of understanding how swamp wallabies are surviving in urban environments, he and Ben-Ami focussed on how roads are impacting on individual animals.

They used radio collars to track the movements of wallabies for three months, and animals were also caught and measured.

The researchers compared nine wallabies living around the M1 freeway, with more than 20 wallabies living in a nearby nature reserve.

Ramp says he thought animals that living near the roads would be having a harder time than individuals that lived elsewhere, but instead he found these animals were fatter for their age than wallabies that lived elsewhere.

"We found surprisingly that both male and female wallabies that were living directly adjacent to the freeway were actually in better body condition than those within the reserves," he says.

The animals also had a smaller range suggesting they were quite happy to hang around the roadside.

The researchers think the most likely reason for this is that the animals get everything they need in the roadside habitat, which is richer in food due to water and nitrogen compounds running off the road, which stimulate plant growth.

"Roads have a lot of runoff and that can actually promote highly nutritious growth and we know that is an attractant for many animals to roadsides," says Ramp.

He says roadside environments can be likened to "ecological traps" that attract animals to them with shelter and food, but that also have a predator running down the middle of them - in the form of cars.

"It's the garden of Eden with the devil standing nearby," says Ramp.

Interestingly, roadside-dwelling male wallabies appeared to benefit in terms of weight more than the females.

Ramp says this is probably because normally females push males to poorer food environments, such as ridge tops, and so males had most to gain from moving to the roadsides.

Streetwise wallabies?

Ramp says only one of the roadside wallabies ventured to the other side of the freeway, apparently using an underpass.

"I think that these particular animals that have set up their residence next to this road are streetwise," he says.

He suspects the animals that are still being killed on the roads are younger males that are on the search for a home, or animals that are on the move for other reasons.

While some individual swamp wallabies make the most of living on roadsides, Ramp emphasises the message is not that roads are an overall good development for wallabies.

"We can't ignore the fact that roadkill is having a major impact on their populations," he says.

Ramp says given swamp wallabies have shown they are a hardy species that can actually share territory with humans, it would be beneficial to encourage fences along roads and underpasses to help preserve the remaining populations.

Tags: conservation, marsupials