Response of koalas (Phascolarctos cinereus) to re-introduction to the wild after rehabilitation
Ellis, WAH, White, NA, Kunst, ND & Carrick, FN 1990, Australian Wildlife Research, vol. 17, no. 1, pp. 421-426.
Four subadult koalas that received treatment for vehicle-related injuries over a two-month period were subsequently released back into the wild and their movements monitored using radio collars. The resident population of 30 koalas at the release site was also being monitored, allowing researchers to observe its response to the released individuals.
The movement patterns of the released koalas appeared to vary between the sexes. After release, females were observed to remain within the vicinity of the release site, whereas males gradually moved away from the release site. Simultaneously, the resident koala population demonstrated no changes in movement patterns in response to the released animals. It is likely that the movement of males away from the release site was due to pressure from dominant males in the resident population. This assertion is supported by the observation that males were making use of non-Eucalyptus tree species, suggesting released males were excluded from preferred trees. Females, on the other hand, seemed to be well-tolerated by dominant males.
Although sick or injured wild koalas can be rehabilitated and released, the fate of released koalas is not commonly monitored. The ecological viability and cost-effectiveness of reintroducing koalas into the wild are therefore poorly understood. Similarly, the impacts of releasing koalas on the resident population are unclear.
To intervene in declining koala populations in south-east Queensland, measures including reintroductions, translocations and breed-and-release programs have emerged as possible ways to restore numbers of the threatened species. If such interventions are to be feasible in the future, further research must be undertaken to better understand the factors that affect the long-term survival of both released koalas and the resident koala population.
Summarised by Joanna Horsfall
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