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Australia has the worst mammal extinction rate in the world, having lost 34 mammal species in the past 200 years. To prevent other threatened mammals from disappearing, the Australian Wildlife Conservancy is returning them to their former ranges. Jennifer Anson, who is coordinating the project, tells ¿ìè¶ÌÊÓƵ it has been a big success.

Alice Klein: Why does Australia have such an abysmal mammal extinction record?

Jennifer Anson: The primary driver is predation by feral cats and foxes that were introduced by Europeans 200 years ago and have spread across the continent. Small- to medium-sized native mammals are just unaware of how to deal with these sorts of predators, so they’re very vulnerable. There’s also very little predation pressure that’s exerted on foxes and cats because we don’t have a lot of predators in Australia that are bigger than them, apart from the dingo.

How many native mammals have you reintroduced and where?

We focus on species that are threatened or going extinct in the wild and try to restore them to parts of their former ranges. In the last 30 years, we’ve reintroduced 6500 individual animals belonging to 19 species. These include the greater bilby, brush-tailed bettong, mala, bridled nail-tail wallaby and numbat.

We have eight sites where we reintroduce these mammals. These must be fenced to exclude foxes and cats, but some are very substantial in size. For example, our Newhaven site in the Northern Territory is 94 square kilometres. That means that free-ranging wild populations can establish within these fenced areas.

How do you know if a reintroduction has been successful?

We fit a subset of animals with radio or GPS collars so we can track their movements and set up camera traps [devices that photograph animals walking past]. We also catch animals and measure their weight, check if they have pouch young and look at other health parameters.

How have the animals fared so far?

We have had great success with the reintroductions. For example, we reintroduced 334 greater bilbies at our Scotia site in 2010, and by 2015 there were over 1200. We now have greater bilbies at five of our fenced sites across three states, protecting around 10 per cent of the species’ total population.

In August and September, we reintroduced 70 brush-tailed bettongs to our Newhaven site and a further 70 individuals to our Mallee Cliffs site. This species used to be across more than half of Australia, but has suffered massive range collapses and is now restricted to the south-west corner of Western Australia. This is the first time they’ve been in the Northern Territory for 60 years. So far, they’re going really well.

Have any reintroductions failed?

Shortly after we did a trial numbat reintroduction to Newhaven, there was a record-breaking heatwave and they just couldn’t survive. We had to scoop up the remaining animals and return them to their source population. We identified that we need to introduce digging mammals like bilbies and bettongs first because they dig underground burrow systems that other animals like numbats can shelter in.

Have the reintroductions been good for other animals and plants?

Yes, we’ve found that populations of other native mammals have also increased within the fenced areas. Native vegetation also benefits because the digging mammals promote seed dispersal and germination.

Do you have any upcoming reintroductions?

We’re keen to establish a secure population of northern bettongs because there are fewer than 1000 individuals left in the wild. We’re currently fencing off a 95-square-kilometre area in north Queensland where we will try to establish a population next year. Setting up these sites is a lot of work. After you build the fence, you have to spend a lot of time intensively removing every single fox and cat inside. The fences then have to be patrolled and checked regularly to ensure they remain feral predator free.

Will it ever be possible to re-establish populations of native Australian mammals outside fenced protection areas?

There is a lot of great research happening looking at ways of eliminating feral foxes and cats, like gene drive technology, but that’s long-term work. For now, threatened native mammals just won’t be able to persist in most areas outside these fences. Our goal is to establish self-sustaining and genetically diverse populations so that if the option ever becomes available, we’ll be able to release them into a fox- and cat-free landscape.

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