A rock-rat in a hard place

By Danae Moore, Wildlife Ecologist and Joey Clarke, Senior Science Communicator

The stars are out, but the tumbled slabs of quartzite are still warm when one of Australia’s rarest mammals emerges from a little crevice to begin its night-time activity, whiskers twitching in the cold night air. It’s looking for food and conditions are good; two years of decent rainfall in Central Australia has triggered a burst of plant life, including flowering shrubs and grasses which produce nutritious seed in abundance. The Central Rock-rat (Zyzomys pedunculatus) is a species teetering on the edge of oblivion. Over the past two decades, the population has fluctuated in response to alternating periods of high and low rainfall, and in recent years the NT Government has been implementing a targeted baiting program to reduce feral cat numbers near known colonies. After years oscillating back and forth on the edge of existence, this is boom time for the Central Rock-rat. For the ecologists trying to prevent Australia’s next mammal extinction, the time to act is now or never.

Brad Leue/AWC

Australia’s native rodents include some of the country’s most remarkable mammal species – from accomplished engineers who build elaborate homes of sticks or stones, to the giant White-tailed Rat which can chew through tin cans. There’s the aquatic Rakali which swims along hunting for yabbies and mussels, and fleet-footed hopping mice, leaving their tracks across the dunes as they bound through the sandy country of the inland. These rats and mice may struggle to capture public attention in the same way as Koalas or Bilbies, but they include some of our most imperilled species.

The rock-rats in the genus Zyzomys are a group of five species, three of which are classed as threatened, found across the more rugged pockets of central and northern Australia. Four are relatively large, weighing about the same as a cricket ball, with a long, thick tail used to store fat – a helpful adaptation during lean times in the arid zone.

Once found across a broad swathe of Central Australia, the Central Rock-rat has disappeared from more than 95% of its pre-European distribution. For decades it seemed to have disappeared completely and was presumed extinct until a tiny population was rediscovered in 1996, clinging to the steep slopes of the West MacDonnell Ranges in Tjoritja National Park near Alice Springs. In 2018, it was assessed as the mammal most likely to become extinct in the next two decades – the clearest signal yet that it was time to intervene to save the species. AWC had previously identified the rock-rat as a prime candidate for translocation to the 9,450-hectare feral predator-free fenced area at Newhaven Wildlife Sanctuary, which lies within their historical range. At Newhaven, Australian Wildlife Conservancy (AWC) has been restoring healthy fire patterns and managing feral animals for more than a decade to improve ecological health.

This year, over five nights in the last week of July, a joint team of ecologists and zoologists from AWC and the NT Flora and Fauna Division and Parks and Wildlife Division, endorsed by Traditional Owners, trapped rock-rats from sites across Tjoritja National Park and airlifted them to Newhaven.

Brad Leue/AWC

The translocation required some high-level logistics involving a Jet Ranger helicopter, six vehicles and more than a dozen people working across five sites in some of the most precipitous terrain in Central Australia. Teams and field equipment were flown into the more remote locations to establish trapping sites across Chewings and Heavitree Ranges, 60–85 kilometres west of Alice Springs. At dusk, the teams set small aluminium box traps, baited with peanut butter and oats, and returned at daybreak to check the traps and collect the rock- rats. Animals were bundled carefully into pet packs then transported to Ormiston Gorge Ranger Station, where DNA samples were taken for an assessment of the population’s genetic diversity.

From Ormiston Gorge, 58 of the rock-rats were transferred 185 kilometres, 90 minutes by helicopter, directly to the top of Wardikinpirri Range, a 10-kilometre-long quartzite outcrop that sits within the fenced area at Newhaven. As the sun set, they were released into suitable habitat identified by the AWC team: small rocky gorges with abundant crevices close to country that’s been burnt within the past few years. Fire history was an important consideration, as fires promote the growth of some important food plants for the rock-rats.

Brad Leue/AWC

In addition to the Central Rock-rats released at Newhaven, 16 individuals were taken to Alice Springs Desert Park, where they will become founders of a new captive breeding program that hopes to boost numbers for subsequent releases. The translocation to Newhaven, coupled with the captive breeding colony, aims to help secure the future for this species – potentially making the difference between survival and extinction – and this highly significant conservation project is supported by funding from the Australian Government. If the new population becomes established throughout the rocky ranges, it is predicted that Newhaven could support a population of around 800 Central Rock-rats in ideal conditions. This is the sixth species translocated to Newhaven, one of the world’s most important rewilding projects.

Watch the video to hear from the team on the ground during this high-stakes translocation.

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