The cause and effect of bat wing tears in common pipistrelle bats (pipistrellus pipistrellus)

Khayat, Rana Osama (2019) The cause and effect of bat wing tears in common pipistrelle bats (pipistrellus pipistrellus). Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Bats represent a quarter of all mammalian species and play vital roles in many ecosystems. They are also are the only mammals capable of powered flight and have large, light, thin wings to enable flight. However, bats face many threats, including collisions with man-made structures, fungal infections and predator attacks, all of which can cause severe wing injuries. Hundreds of bats are admitted annually for care to treat torn and injured wings. This thesis aims to investigate the causes and effects of bat wing tears. In a series of studies, this thesis will: i) characterise wing tears in P. pipistrellus and other bat species in the UK; ii) explore the anatomy of the wing in P. pipistrellus, and see if knowledge of the anatomy is sufficient to understand wing tear placement and healing rates; iii) present a novel method for analysing flight from high-speed video data to assess the effect of tears on flight; and iv) develop a systematic forensic method to identify the presence of cat DNA on wing tears. Results from Chapter 2 indicate that most tears occurred in the Plagiopatagium wing section (section P), which is closest to the body. Tears in that section also might take longer to heal. Chapter 3 suggested that knowledge of wing anatomy is not sufficient to explain tear position and orientation. Indeed, while material testing did not identify section P as being significantly weaker than the chiropatagium (the distal sections of the wing), section P tended to have the most tears. The position of the tears, close to the body and towards the trailing edge, may suggest that they were caused by predator attacks, such as from a cat, rather than collisions. Consistent with this, 38% of P. pipistrellus individuals had confirmed wing tears caused by cats, with an additional 38% identified by rehabilitators as due to suspected cat attacks. Results from high-speed video footage collected in the fourth chapter revealed that tears on both wings significantly affected wing movements, and the body orientation tended to lean towards the healthier wing. The fifth chapter developed techniques to identify cat DNA from swabs of wing tears, and found cat DNA on 66.67% of the swab samples. Results from this thesis reveal that cat attacks on bats may be far more common than first thought. In addition, future work should focus on the seasonal timings of wing tear injuries to structure recommendations for cat owners and model the implications of cat attacks on bat populations. In addition, while the tear injuries do heal, post-release monitoring is important to ensure bats survive in the long-term following rehabilitation. Recommendations for bat carers and cat owners formulated in this thesis are the first steps in addressing the prevalent and significant problem of bat wing tears.