Lutra 52(2)_Haarsma & van Alphen_baldness & pond bats_2009

Partial baldness in relation to reproduction in pond bats in the Netherlands

Temporary bald spots in mammals are usually related to moult. Alternatively, they may be a sign of bad health, or a side effect of hormones. Pond bats (Myotis dasycneme) commonly show partial baldness. Using data from more than 2,200 pond bats, captured between 2003 and 2008, we investigate the possible social, ecological and physiological factors involved in this phenomenon. A large proportion of pond bats were partly bald during a short period of the year, mainly between mid-May and the first week of August. Hair loss was observed in just a small area on the back of the bat, between the shoulder blades. These bald spots were much more common among females than males. The occurrence of baldness was temporally correlated with the nursing period of females. To test the generality of these patterns we studied animals from museum collections and photographs of roosting animals taken during the past two decades. While these data remain anecdotal, the position of the bald spots and the timing of appearance are consistent with those found in this study.