A hairy situation: The diversity of bat wing pelage and its functional implications

Bats are the only mammals capable of true flight. Their wings are primarily hairless, although many bats have varying amounts of pelage distal to the trunk. Little research has investigated how wing pelage varies across bat species or the potential ecological correlates of that diversity. We hypothesize that wing pelage variation among bat species is correlated with body mass and thermoregulatory needs, which may vary among roost ecologies. Using images of wings from 98 species representing 12 families, we qualitatively analyzed pelage distribution along the dorsal and ventral surfaces of the wing membrane and forelimb. We used phylogenetic regressions and principal component analysis to evaluate the relationship between body mass, roost type, sociality, and diet on pelage in each region, finding significant effects of these factors in the extent and distribution of pelage along the patagium and limb. We suggest that wing pelage may be important for insulation despite potential aerodynamic costs. This study provides insight into the distribution of pelage in a diverse selection of bat species, establishing a foundation for future research to explore morphological tradeoffs that may be advantageous for thermoregulation but incur other costs.