Occupancy patterns of the introduced, predatory sugar glider in Tasmanian forests

Introduced mammals pose serious threats to native island fauna, and
understanding their distributionis fundamental to evaluating their
conservation impact. Introduced sugar gliders (Petaurus breviceps) are the
mainpredator of critically endangered swift parrots (Lathamus discolor) on
mainland Tasmania. We surveyed sugar gli-der occurrence over~800 km2in an
important swift parrot breeding area, the Southern Forests. During 4–5
vis-its per site, we used call broadcast of predatory owls to elicit sugar
glider alarm calls and surveyed 100 sitesduring February/March 2016.
Na€ıve occupancy by sugar gliders was high (0.79), as was
detectability(0.520.03 SE), resulting in a cumulative detection
probability of effectively 1. Occupancy modelling indicateda positive
effect of the proportion of mature forest cover on occupancy. The best
model, based on AIC scores,included the proportion of mature forest cover
within a 500 m radius with constant detectability. Our studyrevealed
surprisingly high rates of occupancy of available forest habitat
throughout the heavily logged study area,such that even when mature forest
cover was<10%, sugar glider occupancy was>0.5; where forest
coverapproached 100% (i.e. in the best quality breeding habitat for swift
parrots), occupancy by sugar glidersapproached 1. Our results reveal that
sugar gliders are widespread across the study area which may be
indicativeof occupancy rates elsewhere in the breeding range of the
critically endangered swift parrot. As a result, the riskof predation by
sugar gliders for small birds may be widespread across logged Tasmanian
forests. Additionalwork to identify whether population densities of sugar
gliders vary with forest cover (and whether this mayimpact predation
likelihood) is critical to understanding the conservation consequences of
deforestation in thebreeding range of the swift parrot.