The post-release fate of hand-reared orphaned bats: survival and habitat selection

Abstract

Although bats are frequently admitted to rescue centres — mainly as orphans — very little information is available on their survival after release. Our study answered the following questions: i) do hand-reared bats survive over a short time; ii) which activities and habitat selection do they exhibit; iii) are bats loyal to the release area; and iv) are they able to join local colonies? We radio-tracked 21 hand-reared Pipistrellus kuhlii over a two-year period released on a site that differed from that where they were rescued. At the study site they were provided with the same bat boxes used in the rehabilitation room. Nineteen bats were confirmed to survive, stay in the area and actively forage over 4–14 days. Fourteen day roosts in buildings (nine of which hosted a local colony) were used by 12 subjects. Bats travelled less than 5 km in total each night; their most frequent activity was night roosting, followed by foraging and commuting. We recorded typical foraging behaviour, including hunting around street lamps at sites exploited by many conspecifics. A comparison of habitats available within individual home ranges with those within the study area showed that urban areas, riparian vegetation and farmland were equally important and preferred to woodland. When the foraging time spent in each habitat was compared with habitat composition within individual home ranges or within the study area, urban sites were preferred for foraging over all other habitats, followed by farmland and woodland and finally riparian vegetation. Overall, we showed that hand-raised orphaned P. kuhlii may readily adapt to environments they are not familiar with, exhibit a high short-term survival and select key resources in the release area, provided appropriate rehabilitation and training techniques are adopted.