Resident wild koalas show resilience to large-scale translocation of bushfire-rescued koalas

Julian E Beaman; Connor Mulligan; Claire Moore; Dana Mitchell; Edward Narayan; Karen Burke da Silva

doi:10.1093/conphys/coac088

Resident wild koalas show resilience to large-scale translocation of bushfire-rescued koalas

Conserv Physiol. 2023 Jan 28;11(1):coac088. doi: 10.1093/conphys/coac088. eCollection 2023.

Authors

Julian E Beaman¹, Connor Mulligan¹, Claire Moore¹, Dana Mitchell^{2

3}, Edward Narayan⁴, Karen Burke da Silva¹

Affiliations

¹ College of Science and Engineering, Flinders University, Bedford Park, South Australia 5042.
² Kangaroo Island Wildlife Park, 4068 Playford Hwy, Duncan, South Australia 5223.
³ Kangaroo Island Koala & Wildlife Rescue Centre, 4068 Playford Hwy, Duncan, South Australia 5223.
⁴ School of Agriculture and Food Sciences, The University of Queensland, Lawes, Queensland 4343.

Abstract

Wildlife translocation is increasingly utilized as a conservation management action, to mitigate the immediate negative effects of habitat loss and fragmentation (e.g. from land clearing or bushfires). Previous research has shown that stress responses can help or hinder survival in translocated wildlife and determine the efficacy of translocation as a conservation action. Yet these translocated animals are only one side of the equation, with translocation also potentially impacting the animals in the recipient population. We measured physiological markers of stress (faecal cortisol metabolite concentrations and neutrophil-lymphocyte ratios) and assessed health condition in a wild koala population one year after a major translocation of bushfire-rescued koalas on Kangaroo Island. We expected to find a high population density at the site (>0.75 koalas per hectare) and that resident koalas would show signs of chronic stress and ill health as a result of territorial conflict over food trees and reproductive opportunities. In contrast, we found that only one-fifth of the population remaining at the site were translocated koalas. The overall population density was also much lower (0.21 koalas per hectare) than anticipated. With no evidence of mass mortality at the site, we suggest that the majority of translocated koalas dispersed away from the site. Our stress marker measurements did not differ between the wild koalas and a sample of captive (non-display) koalas at the nearby Kangaroo Island Wildlife Park and were generally low compared to other studies. Veterinary examinations found that most koalas were in good body condition with very few diagnostic indicators of systemic ill health. Overall, our results suggest that, if there is adequate landscape-scale habitat connectivity and opportunity for dispersal, translocated koalas are likely to disperse from the site of release, with limited impacts on recipient koala populations at translocation release sites.

Keywords: Wildlife conservation; wildlife health; wildlife management.