Population monitoring of an endemic macropod, the quokka (Setonix brachyurus), in the northern jarrah forest, Western Australia

Abstract

Monitoring populations of threatened species plays a part in continued conservation and contributes to assessment of how effective management actions are. We estimated population indices and studied cohort demographics of mainland populations of quokkas (Setonix brachyurus) at 14 sites across the northern jarrah forest. One site is currently monitored through annual trapping, seven were intensively surveyed a decade previously, while six sites had no previous monitoring. Across the 14 study sites, no quokkas were detected at one site and the other population estimates ranged from 5 to 25 adults. Most females (86% of capture events) carried a pouch young or were lactating (indicating a young at foot). Quokka populations at the eight previously-surveyed sites showed variable population changes. We discuss likely contributing factors, including broad-scale fox baiting and fire. Comparative studies of native species over time are important; however, such comparison has limited capacity to explain population changes without comparable methods or where relevant contributing factors (e.g. predator numbers, habitat change) have not likewise been monitored. The threat of changing climate in the northern jarrah forest (where increasing temperatures and greater frequency of drought have been witnessed over the last decades) and implications for control of fire regimes increases the urgency for an updated review of quokka populations to guide appropriate management actions.