RISKIN, D.K.*; HERMANSON, J.H.; BERTRAM, J.E.A.; Cornell Univ.; Cornell Univ.; Florida State Univ.: The role of the hindlimbs in non-aerial locomotion of bats

While a few bat species like the common vampire (Desmodus rotundus) crawl and jump in a coordinated fashion, bats like Pteronotus parnellii and Carollia perspicillata crawl very poorly, and others like Macrotus californicus and Mormoops megalophylla appear almost entirely unable to crawl. Previous authors have noted that bats with relatively robust hindlimbs crawl better than thin-legged bats, and have suggested that the reduced hindlimbs of many bats preclude them from terrestrial locomotion. However, the role of the hindlimbs in non-aerial locomotion in the poorly-crawling bats is not known. If they are used to transmit forces to the substrate, their reduction could hinder locomotion, however if the hindlimbs are dragged passively behind the forelimbs, then reduction of the hindlimb skeleton would ameliorate crawling. Using a force platform and digital camera recording at 250 Hz in 117 trials, we (1) documented the non-aerial locomotor behaviour of 7 bat species (n=9): three phyllostomid frugivores (Artibeus jamaicensis, A. lituratus, C. perspicillata), two phyllostomid sanguivorous (D. rotundus, Diaemus youngi), and two mormoopid insectivores (M. megalophylla, P. parnellii); and simultaneously (2) quantified the roles of the hindlimbs in the crawling and jumping locomotion of those individuals. We found that the hindlimbs of �poorly-crawling� bats contribute to locomotion by transmitting vertically and horizontally oriented forces to the substrate. Quantification of these trends is ongoing. Our qualitative results support the hypothesis that reduced hindlimbs hinder non-aerial locomotion. Video analyses also revealed that the forelimbs moved differently in the good-crawlers (D. rotundus and D. youngi) than they did in any of the other bats studied. The morphology of the pectoral girdle may also influence crawling ability.