A systematic review of factors affecting wildlife survival during rehabilitation and release

Abstract

Millions of native animals around the world are rescued and rehabilitated each year by wildlife rehabilitators. Triage and rehabilitation protocols need to be robust and evidence-based, with outcomes consistently recorded, to promote animal welfare and better understand predictors of wildlife survival. We conducted a global systematic review and meta-analysis of 112 articles that reported survival rates of native mammals and birds during rehabilitation and after release to determine intrinsic and extrinsic factors associated with their survival. We assessed survival during rehabilitation and in the short- and long-term post-release, with the hypothesis that survival will vary as a function of species body size, diel activity pattern, trophic level and study location (region of the world). We aimed to determine the direction of effect of these factors on survival to assist in decision-making during triage and rehabilitation. Results showed that mammals and birds were equally likely to survive all stages of rehabilitation, and survival rates varied between locations. Birds in North America had the poorest survival rates post-release, particularly long-term, as did diurnal and carnivorous birds in the short-term post-release. Anthropogenic factors such as motor vehicle collisions and domestic or feral animal attack contributed to morbidity and post-release mortality in 45% (168 of 369) of instances. The reasons for rescue and associated severity of diagnosis were commonly reported to affect the likelihood of survival to release, but factors affecting survival were often species-specific, including bodyweight, age, and characteristics of the release location. Therefore, evidence-based, species-specific, and context-specific protocols need to be developed to ensure wildlife survival is maximised during rehabilitation and post-release. Such protocols are critical for enabling rapid, efficient rescue programs for wildlife following natural disasters and extreme weather events which are escalating globally, in part due to climate change.

Outcomes for an arboreal folivore after rehabilitation and implications for management

“…Our study found an annual survival rate of 58.5%, comparable to survival rates of other rehabilitated koalas (e.g., 58% survival 43 ), but lower than some wild living populations (e.g., 92.5–74% survival 77 ) which indicates that techniques for improving outcomes for koalas in care are much needed. We discuss a range of recommendations below, which contribute to the identified need for evidence-based and context specific protocols to maximise outcomes for rehabilitated animals 78 . We found that including basic assessments that don’t require any specialist equipment (e.g., body condition and climbing ability scores) can improve post-release survival rates.…”

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

“…Our study identi ed several critical areas where rehabilitation and release procedures can be improved, which are easily implemented and applicable to a range of different species. We discuss a range of recommendations below, which contribute to the identi ed need for evidence-based and context speci c protocols to maximise outcomes for rehabilitated animals 72 . We found that including basic assessments that don't require any specialist equipment (e.g., body condition and climbing ability scores) can improve post-release survival rates.…”

Causes of Raptor Admission to the Wildlife Rehabilitation Centre in Abruzzo (Central Italy) from 2005–2016

“…For example, it is known that male sparrowhawks were less likely to be released than females [ 17 ], and that male raptors are more susceptible to spontaneous mortality than females [ 73 ]. Factors influencing survival rates before and after revival have been reviewed by Cope et al [ 74 ] and should be used as a framework to guide rescue and treatment protocols, tailored to each species and based on global evidence of effectiveness. With these robust protocols in place, veterinarians and rescue organizations can continue to minimize animal suffering and maximize the effectiveness of rehabilitation programs in an increasingly anthropogenically expanding world with increasing climate change [ 74 ].…”