2. Getting to know Northern Bettongs: Population, Foraging and Nesting

Getting to know Northern Bettongs: Population, Foraging and Nesting

Research by PhD Candidate: Tegan Whitehead (Research Grant 2013, 2014, 2015)

The northern bettong, Bettongia tropica, endemic to the Queensland Wet Tropics Bioregion, has a fragmentedpopulation along the western edge of the Bioregion. B.tropica is listed as Endangered under the Nature Conservation Act 1992 (Qld) and the Environmental Protection and Biodiversity Conservation Act 1999 (Cth). It is also ranked as critical priority in the “Back on Track species prioritisation framework” (Department of Environment and Heritage Protection). The diet of B.tropica consists heavily of truffles (underground fungi) and cockatoo grass Alloteropsis semialata and also includes other grasses, roots, tubers, seeds, leaves and insects.

In this study “Population abundance, microhabitat resource use and ecology of the northern bettong” three known B.tropica sites were identified across the Lamb Range: Tinaroo Dam, Davies Creek and Emu Creek. The objectives of this project were to determine the population status at each site; the abundance of potential predators and competitor species and to assess the microhabitat resource use and foraging behaviours of B.tropica. The methods used to collect data in this study include cage trapping and camera trapping, GPS collar tracking, oort sampling and site surveys for nests and diggings.

Data indicate that the highest population density in the study area occurs at Tinaroo Dam, followed by Emu Creek and then Davies Creek. The population densities recorded are similar to estimates from twenty years ago (reported in Vernes and Pope 2006) indicating that the sub-populations across the Lamb Range have remained stable.  

Using GPS tracking, the study found that B.tropica foraged at steep sloping sites with an abundance of cockatoo grass. Whitehead links this preference of site selection to availability of food and predator avoidance with known predators often inhabiting the top of ridgelines. Sites where the Rufous Bettong (Aepyprymnus rufescens) were identified are linked with a decrease in the capture of B.tropica indicating a competitor relationship. Similarly for some site where predators were detected, B.tropica were not. It was also found that with increased rainfall (used as a proxy for food abundance) that the home range of B.tropica would decrease and that male B.tropica were found to travel further and faster than females.

Nesting habitats of B.tropica were surveyed across the three sites and it was found that nesting sites were more likely to occur at sites with increased grass cover and grass tree density. Nests were constructed from grass and often constructed under the ‘skirts’ of grass trees. At the Tinaroo Dam site ‘tepee’ shaped nests made from sticks and grass were found which has not previously been recorded for B.tropica. These nests were found within Allocasuarina or lantana thickets which are considered sub-optimal habitats and may reflect limited availability of Eucalyptus woodland, the preferred nesting areas for B.tropica. This may help inform future vegetation management plans within the known habitat of B.tropica to ensure that suitable habitats are available for the species to nest and forage.