Bilby Bernard DupontAustralia’s shy endangered marsupials will have a far better chance of surviving deadly predation by feral cats and foxes if they are kept in several protected areas instead of a single large area, scientists say.

Fences are a key strategy in the conservation of threatened native species, particularly in Australia and New Zealand. But what do you do if your fence is too successful? 

Australia has more than 37 large conservation fences, enclosing 27 species of bird, marsupial and reptile in more than 35,000 hectares of predator-free habitat.

On the Australian mainland, many of these species can no longer be found outside chain-link and electrified wire. To save the greater bilby, for example, a predator-proof fence was built in Queensland’s Currawinya National Park, enclosing 25 square kilometres. State governments and conservation nongovernmental organisations (NGOs) such as the Australian Wildlife Conservancy are all planning to extend the use of fenced reserves to protect other endangered terrestrial wildlife.

Although these species have been driven to the brink of extinction by cat and fox predation, they are perfectly adapted to the Australian environment.  Once they’re protected behind a fence, their numbers can increase dramatically. Where do you put all the excess animals?

After a while then, all managers face the same dilemma: do they expand existing successful fence projects, which would be easier and cheaper to manage, or do they set up new fenced areas somewhere else?

Kate Helmstedt, a CEED PhD student who now works at the University of California, Berkeley, showed this year that extra funds should almost always be used to build new, separate fenced areas. This is in stark contrast to the current practice, which is to use money to expand the existing fences in a series of renovations. Separate fences split the risk of catastrophes: protecting our highly vulnerable animals against feral cats, dogs and foxes, diseases, or catastrophes such as fires and floods.

Helmstedt’s new method gives clear advice. If the managers can find a suitable location that’s within 60 km of their existing project, they should build a second fenced area. Fences that are more than 60 km apart cost too much money to manage over the long term. If no suitable locations exist closer than 60 km, then managers should enlarge their existing fence.

 

Research theme: Quantitative tools and approaches (E)

Photo: Bernard DuPont, Flickr CC