DOI: 10.5061/dryad.jwstqjqnk
title: Data from: Vulnerability of a small population of an arboreal mammal to landscape change associated with a new motorway and drought

description: 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 (&gt; 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.
description: # Data from: Vulnerability of a small population of an arboreal mammal to
 landscape change associated with a new motorway and drought Dataset DOI:
 [10.5061/dryad.jwstqjqnk](10.5061/dryad.jwstqjqnk) ## Description of the
 data and file structure Spotlight survey data - We conducted surveys three
 times in each of six years over 10 years: 2014, 2016, 2018, 2019, 2021,
 2023. Spotlight surveys were conducted along a 200-m-long transect over 20
 minutes. Spotlighting was used because it is a general survey technique
 for nocturnal arboreal mammals in Australia. Spotlighting was conducted by
 a single person who walked at a slow speed (600 m per h) and illuminated
 the forest on both sides of a transect using a flashlight torch (producing
 350 or 600 lumens). Any arboreal mammals seen or heard calling were
 recorded. At the halfway mark, four recorded calls of the yellow-bellied
 glider and the powerful owl (*Ninox strenua*) were broadcast from a
 portable speaker, loud enough for yellow-bellied gliders within at least
 200 m of the transect to hear. The powerful owl may occasionally prey on
 the yellow-bellied glider, and its call can provoke a vocal response.
 Transects were surveyed on three different nights each year, at least two
 weeks apart, between August and December. Surveys were usually conducted
 under ideal conditions of no rain, low moonlight, and limited wind, and 1
 to 5 h after dark. From the survey data, a detection history of 18 survey
 occasions was generated for the yellow-bellied glider and sugar glider
 that described whether the species was detected (1) or not detected (0).
 ### Files and variables *
 Nambucca-Yellow-bellied-glider-detection-histories.csv Yellow-bellied
 glider detection histories - 92 survey sites (rows in the data) with 18
 survey occasions (columns in the data). The surveys are indicated by a
 year-survey notation covering 6 years across 10 years (i.e., 1.1, 1.2,
 1.3, …, 10.1, 10.2, 10.3). * Nambucca-sugar-glider-detection-histories.csv
 Coastal-sugar-glider-detection-histories -same as yellow-bellied glider.