Invasive predators represent the greatest extinction threat to the endangered northern bettong (Bettongia tropica)

Abstract

Context. Identification of key threats to endangered species is vital for devising effective management strategies, but may be hindered when relevant data is limited. A population viability approach may overcome this problem. Aims. We aimed to determine the population viability of endangered northern bettongs (Bettongia tropica) in northeastern Australia. We also assessed the key threats to the population resilience and how the population viability responds to increases in mortality rates and changes in fire and drought frequency. Methods. Using population viability analysis (PVA) we modelled survival probability of B. tropica populations under likely scenarios, including: (1) increased predation; (2) changes in drought and fire frequency predicted with anthropogenic climate change; and (3) synergistic effects of predation, fire and drought. Key results. Population viability models suggest that populations are highly vulnerable to increases in predation by feral cats (Felis catus), and potentially red fox (Vulpes vulpes) should they colonise the area, as juvenile mortality is the main age class driving population viability. If B. tropica become more vulnerable to predators during post-fire vegetation recovery, more frequent fires could exacerbate effects of low-level cat predation. In contrast, it was predicted that populations would be resilient to the greater frequency of droughts expected as a result of climate change, with high probabilities of extinctions only predicted under the unprecedented and unlikely scenario of four drought years in 10. However, since drought and fire are interlinked, the impacts of predation could be more severe with climate change should predation and fire interact to increase B. tropica mortality risk. Conclusion. Like other Potoroids, B. tropica appear highly vulnerable to predation by introduced mammalian predators such as feral cats. Implications. Managers need information allowing them to recognise scenarios when populations are most vulnerable to potential threats, such as drought, fire and predation. PVA modelling can assess scenarios and allow pro-active management based on predicted responses rather than requiring collection of extensive field data before management actions. Our analysis suggests that assessing and controlling predator populations and thereby minimising predation, particularly of juveniles, should assist in maintaining stability of populations of the northern bettong.