An analysis of the long-term trends in the records of Friends of the Koala in north-east New South Wales: II. Post-release survival

Abstract

Context Post-release monitoring of rehabilitated koalas is lacking, meaning that the long-term success rate is unknown. Aims We addressed the question: will a koala released from rehabilitation re-join the wild population and survive for months, if not years? Methods Using ear tag records as unique identifiers of individual koalas, we sifted the 31-year set of 5051 koala admission records (1989–2020) of a koala rehabilitation group, Friends of the Koala, in Lismore, north-east New South Wales for records of koalas that had returned to rehabilitation for a second, third or fourth time. Key results Of the 1771 koalas that were released, most (80%) had a coloured ear tag with a unique number. Of these koalas, 270 were admitted to rehabilitation two or more times and therefore represented an opportunity for post-release monitoring. Re-admission figures mostly fitted the pattern of first admissions, meaning that the released koalas had become part of the local koala population. Of the 270 koalas that were re-admitted into rehabilitation, 66% remained for more than 6 months in the wild, and 33% remained in the wild for more than 2 years. Conclusions We conclude that rehabilitated and released koalas can survive in the wild long-term, even though some koalas were re-admitted after a very brief period post-release. Implications The success of rehabilitation and release, as judged by re-admitted tagged koalas, is a more robust view of success for koala survival after rehabilitation than simply the proportion of released versus non-released koalas.