Subsidiary adaptations: climbing techniques in vespertilionid bats

The quadrupedal locomotion of bats still remains almost unexplored. Meanwhile, in the life of many species, this type of movement plays an important role. This paper presents the study of characteristics of quadrupedal locomotion on vertical surfaces in bats. We provide the results of the analysis of climbing of five vespertilionid species. The study is based on high-speed video recording of locomotion in two planes in an experimental enclosure on various substrates (the bark of five tree species and the inner surface of the manufactured nest box for bats). For comparison, we used data on horizontal locomotion obtained using the same experimental facilities, as well as all available literature data to date. The time, metric and velocity characteristics of the movement of different species representatives are determined. We show how these characteristics are interrelated and how they differ in walking or climbing. The study comparing walking vs. climbing was performed for the second time ever. It is shown that while climbing, bats retain the same limb sequence, but the gait is not a slow trot-like walk but a very slow walk. There are considerably fewer deviations from the usual symmetrical sequence gait (wherein a forelimb movement is followed by that of the contralateral hind limb) when climbing than when walking, and they are all associated with the search for support. Our results show that not all tree-dwelling species of vesper bats can move up the trees which they use to roost. The surface of the inner walls of artificial shelters for bats may be a significant factor in their occupancy. While designing such shelters, it is advisable to consider the results of our experiments or conduct tests on the behavior of particular species on specific artificial surfaces.