Alopecia in Two Species of Insectivorous Bats during the Critical Time Period of Female Reproduction

Abstract - Alopecia in bats has been related to multiple stressors, such as ectoparasite infestations, environmental contaminant exposure, idiopathic disease, and reproductive stress. Here we note occurrences of alopecia in 2 species of insectivorous bats, including a federally endangered species. In the summer of 2022, we encountered 3 Eptesicus fuscus (Big Brown Bat) and 7 Myotis grisescens (Gray Bat) with alopecia during mist-net and harp-trap surveys at multiple locations in Tennessee, USA. Seven of the 10 bats with bald spots were adult lactating or post-lactating females, 1 was an adult pregnant female, and 2 were adult nonreproductive males. No bats with alopecia were encountered after the lactation or post-lactation time period, despite continued mist-net and harp-trap surveys. The cause of the alopecia is unknown and warrants further investigation of prevalence across pre-reproductive (pre-pregnancy), reproductive (pregnancy, lactation, and spermatogenesis), and post-reproductive (pup volancy) periods in these populations. Understanding natural molt cycles versus alopecia as an outward sign of stress in individuals is critical for assessing the health of bat populations.