Insuring woylies (Bettongia penicillata ogilbyi) against extinction: establishment of Perup Sanctuary

Context

Predator free havens are increasingly relied upon to preserve populations of imperilled species, yet despite their substantial cost, the success of these ventures is rarely critically evaluated.

Aims

Based on 12 years of population monitoring data, we report on the translocation of woylies (Bettongia penicillata ogilbyi) to Perup Sanctuary, a 423 ha predator-free haven in the south west of Western Australia.

Methods

We built spatially explicit capture–recapture models to estimate population density, population growth rates, and survivorship of woylies inside the sanctuary. Using these estimates, and additional demographic information, we aimed to show key drivers of population density, evaluate the establishment of the sanctuary population against predetermined translocation success criteria, and run simulations of different sampling designs to determine a robust sampling design for future monitoring of this population.

Key results

The population rapidly increased in the first 3 years (2010–2013), and then fluctuated around a density of ~0.9 woylies ha⁻¹ before declining slightly in recent years to ~0.6 woylies ha⁻¹. All translocation success criteria evaluated were met. The previous 3 months’ rainfall was a key driver of population density and body weight declined over time, indicating that the population may be regulated by food resources.

Conclusions

Woylies have established and persisted in Perup Sanctuary, and against the criteria, the translocation of woylies into Perup sanctuary is a success. Harvests from this population appear to have been sustainable. We discuss these findings in the context of the Perup Sanctuary, and recommend ongoing monitoring continue to ensure that the population remains viable and well managed.

Implications

We describe important considerations for the supplementation and harvest of fenced populations, including: the source of animals (selecting free-living individuals over captive ones); the timing of release (releasing more individuals early on may improve establishment probabilities); and rates of harvest (<30% of adults harvested per generation seemeded to be sustainable for woylies in this case). The results from this study can inform the ongoing management of this and other havened populations, to ensure they continue to benefit mammal conservation.