Fostering hope for wallaby species

By Ken Eastwood 2 October 2012
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An ethically challenging conservation technique may help save an endangered species.

IT’S AN INNOVATIVE way to rescue vanishing species. Though the technique known as ‘cross-fostering’, presents a challenge for animal ethicists, it may be the lesser of two evils.

Cross-fostering happens when a female of an endangered species is mated and becomes pregnant at the same time as a female of a related but non-threatened species. At an early developmental stage, offspring are removed from both the mothers’ pouches and the progeny of the non-threatened species is then euthanised, freeing its mother to raise the endangered young. Meanwhile, the endangered female can quickly become pregnant again (as naturally happens in macropod species), allowing her to produce more offspring than normal – up to an eight-fold increase annually.

During the past decade, Australian researchers have been perfecting the technique for a range of marsupials, including a variety of threatened wombats, potoroos and wallabies. But the largest program, developed by Conservation Ark zoologists Dr David Taggert and Dr David Schultz, is for the southern brush-tailed rock-wallaby, of which fewer than 30 are believed to survive in the wild.

The ACT’s Tidbinbilla Nature Reserve is the site of the accelerated breeding program for the species and uses yellow-footed rock-wallabies and tammar wallabies as foster mums. Senior wildlife officer David Dobroszczyk and his team measure head lengths of newborn, jellybean-sized joeys from five days after birth, and use the measurements to then identify suitable foster mothers with offspring at similar stages of development.

Wallaby foster program helping species survival

Matching the endangered young with foster mums typically requires the careful transportation of newborn joeys as hand luggage (with Civil Aviation Safety Authority approval) to other institutions involved in the program – Waterfall Springs Wildlife Sanctuary on the NSW Central Coast and Adelaide Zoo.

About 70 per cent of the program’s joeys survive to adulthood – a significantly higher rate than in the wild. After about 12 months, joeys are separated from their foster mums and placed with their own species.

In the past two years, 15 brush-tailed rock-wallabies from the program have been released into western Victoria’s Grampians National Park as part of an ongoing reintroduction plan.

David Schultz, a vet at Adelaide Zoo, acknowledges that euthanising pouch young is unpleasant. “But you have to say the end justifies the means,” he says. David Dobroszczyk adds: “If we don’t help this species right now…it will become extinct. If that’s not a call to arms, I don’t know what is.”

As David Taggert points out: “With many of our marsupial species in decline and on the brink of extinction, this technique indeed fosters new hope.”

Source: Australian Geographic (Issue 98, April – June, 2010)