Endangered Northern Bettongs find refuge in Wet Tropics
Australian Wildlife Conservancy together with Queensland Parks and Wildlife Service (QPWS) are forging an exciting alliance to implement a monitoring and research program aimed at protecting Australia’s natural treasures across three national parks in north Queensland’s Wet Tropics Heritage Area. Mt Windsor, Mt Spurgeon and Mt Lewis National Parks, and AWC’s adjacent Brooklyn Wildlife Sanctuary, are known hotspots for biodiversity.
The program, which commenced in 2017, is revealing crucial information about the survival of keystone species like the Northern Bettong (Bettongia tropica).
Priority species, which play a vital role in maintaining forest health, are the focus of particular attention for this innovative initiative between AWC and QPWS.
Northern Bettongs once ranged across a vast area, from central Queensland to the Wet Tropics of northern Queensland. Since European settlement, however, populations of this small marsupial have undergone a catastrophic decline and, in the last few decades, have disappeared from most of their former range. In fact, two of the last four remaining populations have vanished in the last 15 years.
Across the continent, predation by feral cats, changed fire regimes and habitat degradation caused by feral herbivores have driven bettongs to the brink of extinction. So much so that the Northern Bettong is now considered one of the 20 mammal species most likely to go extinct in the next 20 years. Recent surveys indicate the largest of the remaining populations, in the Lamb Range near Cairns, supports fewer than 1,000 individuals.
Northern Bettongs are a keystone species, delivering important ecosystem services in the forest and woodland habitats they occupy. Eating and dispersing a huge diversity of ectomycorrhizal fungi, they are essential for tree health. Their loss spells tragedy for conservation and imputes long- term negative consequences for the ecological communities of which they are part.
Almost all previous research on the Northern Bettong has focused on populations in the Lamb Range, with very little known about the other remaining population in Mt Lewis and Mt Spurgeon National Parks. Historically, Northern Bettongs also occurred on Mt Windsor National Park, but there have been no records since 2003. Extensive camera surveys of Mt Windsor, conducted by AWC and QPWS across 98 sites in 2018, did not detect a single Northern Bettong, suggesting that the Mt Windsor population is now locally extinct.
Fortunately, a population of the species has persisted across Mt Lewis and Mt Spurgeon National Parks.
Camera trapping by AWC and QPWS has detected the Northern Bettong at 39 of 230 sites over only 1,500 hectares.
Trapping surveys conducted by AWC, with the assistance of QPWS and the Traditional Owners, Western Yalanji Aboriginal Cooperation, resulted in the capture of 13 individual Bettongs. Traps covered one third of the site and the results suggest the population is small, perhaps only 50 individuals. Genetic samples were collected to help determine whether the population is maintaining genetic diversity which risks being lost when populations are small due to genetic drift and in-breeding. Baseline health and body condition assessments were also conducted.
One of the known threats to the Northern Bettong is loss of habitat through inappropriate fire regimes. Fire suppression has led to an invasion of rainforest plants and weeds and the loss of a grassy understory. QPWS, which has been managing fire in the area, successfully burnt an area of forest that had been subject to thickening in December 2017. No Northern Bettongs were detected in this area before the fire. However, seven months afterwards, as small patches of grass began to reappear, AWC’s surveys detected Northern Bettongs at a number of sites. These results show Northern Bettongs have recolonised these formerly degraded habitats – an essential step in conserving this small, restricted population.
AWC ecologists have deployed GPS collars on eight Northern Bettongs to track their movements and provide crucial data on home range and habitat use.
These collars recorded the location of bettongs every 20 minutes throughout the night for an entire month. Data collected from the collars is now being analysed.
AWC surveys in the Wet Tropics have also targeted the occurrence and behaviour of feral cats. Camera studies revealed feral cats frequented waterholes and utilised dry creek beds. They avoided roads, perhaps because of the large number of dingoes that seem to prefer using them. Surveys detected feral cats at a much higher frequency at Mt Windsor (where the population of Northern Bettongs appears to have gone locally extinct) than at Mt Lewis and Mt Spurgeon.
Feral herbivores, such as cattle, have adversely impacted Northern Bettong habitat on Mt Lewis and Mt Spurgeon. Cattle have trampled and eroded sensitive plants and heavily grazed the grassy understory.
Northern Bettongs rest during the day in clumps of grass, mainly Kangaroo Grass (Themeda triandra), and they feed on the tubers of Cockatoo Grass (Alloteropsis semialata) during the dry season. Cattle reduce the availability of both food and shelter for bettongs. They also reduce grassy fuel loads, making it difficult for managers to successfully implement fire management. QPWS and Western Yalanji are installing a block fence to reduce the impact of grazing by cattle who wander over from neighbouring pastoral stations.
By joining forces, AWC and QPWS have successfully confirmed the presence of the Northern Bettong at Mt Lewis and Mt Spurgeon, and have improved our knowledge about the key threats to their survival. The data gathered from this project is providing crucial guidance about the land management actions that must be implemented in order to effectively secure the future of this keystone marsupial for all Australians.
This project is supported by the Australian Wildlife Conservancy, through funding from the Australian Government’s National Landcare Program.
Read and download this full issue of Wildlife Matters here.