Factors influencing the success of hand-reared juvenile brushtail possums (

Abstract

Context. Wildlife is ubiquitous in urban environments, resulting in frequent interactions with humans and human infrastructure. The result of these interactions is often negative, in the form of road injury, orphaning of dependent young or eviction from natural home ranges. Wildlife rehabilitation programmes are devised to counter these negative interactions. However, the success of current management strategies is rarely assessed. Aims. We aimed to determine whether short-term survival of juvenile hand-reared common brushtail possums (Trichosurus vulpecula) released in the wild was a function of (1) intrinsic factors such as sex, individual personality and level of human habituation, and (2) extrinsic factors such as release practice (soft vs hard-release) or location (urban vs rural). We also evaluated the relationship between habituation to humans and time spent in care by possums, if presence of conspecifics during the rehabilitation process influenced the development of individual personality, and if this differed in hand-raised animals compared with wild individuals. Methods. We radio-tracked and monitored 20 hand-reared juvenile possums (10 females and 10 males) for up to 40 days after release in the wild. Key results. Eight possums (40%) survived until the end of the study, nine possums (45%) were killed by foxes or had to be returned into care and three possums (15%) had unknown fates (i.e. lost VHF signal). We found that more exploratory individuals and those less human-habituated were more likely to be successful in the wild in both rural and urban areas, whether or not they were hard or soft released. Conclusions. Our results suggest that personality is a key criterion to consider when evaluating the success of rehabilitation programmes. Behavioural traits of hand-reared brushtail possums differed significantly from those of wild individuals, showing that captive conditions can affect the development of personality. Hand-reared possums that spent more time in care were also more likely to display highly human-habituated behaviours. Implications. By demonstrating which factors influence success of hand-reared wildlife after release in the wild, our results help in evaluating current rearing and release practices, and improve the evidence base for developing best practice wildlife rehabilitation guidelines.

Trends in Rescue and Rehabilitation of Marsupials Surviving the Australian 2019–2020 Bushfires

“…Few studies have monitored post-release survival of rehabilitated wildlife, and even fewer have included an experimental design or control group [28]. A study of hand-raised brushtail possums found that 45% of releases were unsuccessful in the first four weeks [86], yet, from a long-term rehabilitation dataset, we know that rehabilitated koalas are capable of surviving in the wild long-term [87]. A study of koalas rehabilitated following fire found that the annual post-release survival rate was 58% compared with 67% for uninjured koalas, and predation by dogs was the leading cause of mortality in both cohorts [88].…”

“…The availability of suitable release locations within a short timeframe can be a challenge, particularly as unburnt habitats are likely to be refuges for fire survivors and already be at capacity. Research on the suitability and feasibility of translocation of rehabilitated wildlife is needed in situations where suitable release locations are limited [28], as keeping animals in care for longer periods will likely increase levels of humanisation, which has been linked with poor post-release outcomes [86].…”

Outcomes for an arboreal folivore after rehabilitation and implications for management

“…Koala admittance to wildlife hospitals had already been increasing over time 9 , 52 , and following the bushfires increased further 10 , 21 . Despite theoretical evidence that rehabilitated animals may contribute to population growth 3 , there is limited empirical data on post-release outcomes for rehabilitated koalas or similar species (e.g., brushtail possums 59 ) to guide investment and decision making in population management.…”

Assessing outcomes for an arboreal folivore after rehabilitation; implications for management.

“…Koala admittance to wildlife hospitals had already been increasing over time 9,52 , and following the bush res increased further 10,21 . Despite an increased need, there is limited data on post-release outcomes for rehabilitated koalas or similar species (e.g., brushtail possums 57 ) to guide investment and decision making in population management.…”