Data from: Vulnerability of a small population of an arboreal mammal to landscape change associated with a new motorway and drought

Small populations are vulnerable to extinction due to extrinsic factors
such as increasing levels of habitat disturbance and isolation, as well as
environmental variation. We investigated the response of a small
population of a nationally threatened Australian arboreal mammal, the
yellow-bellied glider (Petaurus australis; 560 g), to the construction of
a new motorway, which increased the isolation of this population. We
contrasted the small population with two larger populations in
conservation reserves in the broader region. We conducted surveys in 6 of
10 years at 92 sites across the three forest areas to describe changes in
population occupancy. A severe drought occurred in year 6 of our study.
The probability of occupancy in year 1 was lower (0.22) in the small
population compared to the larger reserve populations (0.52). The drought
had a profound influence on all populations, with lower detection leading
into the drought, before detection recovered to pre-drought levels in the
reserves. Additional survey effort using audio-recorders was employed to
detect individuals in the small population of this highly vocal species,
but none were detected 4 years after the drought, suggesting local
extinction had occurred. Whilst motorway construction increased population
isolation, it appears the drought was probably the most consequential
factor given its adverse influence on all populations. The three forest
areas also contained the coastal sugar glider (Petaurus breviceps; 100 g),
which has much larger population sizes (~28 times larger in the small
population area) and a higher reproductive rate compared to the
yellow-bellied glider. Its probability of occupancy (> 0.6) did not
differ among the three populations and was unaffected by the drought. The
contrasting response in the two species highlights the importance of life
history traits when populations are fragmented.