Effects of age and season on body mass and reproductive condition in male Daubenton's bats (Myotis daubentonii)

ENCARNACAO, J. A., U. KIERDORF, V. WOLTERS: Effects of age and season on body mass and reproductive condition in male Daubenton's bats (Myotis daubentonii). Vet. arhiv 76, S239-S249, 2006. ABSTRACT We analyzed the effects of age and season on body mass and reproductive condition in male Daubenton's bats (Myotis daubentonii) from a study area in central Germany, which were captured during April to October of the years 1998-2003. On first capture, animals (n=336) were banded and classified as either young of the year or adults (i.e. males ≥ 1 year of age). On recapture, animals first caught as young of the year could be assigned an exact age in years. Epididymal distension in young of the year indicated that some males had reached sexual maturity (defined as onset of spermatogenesis) already in their year of birth, while others did so in their second summer. Body mass and epididymal distension showed pronounced variation related to age and season, with highest values reached in late summer/early autumn. Generally, older males (>2 years of age) tended to be heavier and in better reproductive condition than younger ones. Our data suggest that the physical condition of male Daubenton's bats, and their reproductive condition, both increase after the initial onset of fertility (start of spermatogenesis) until three years of age. This relatively late physical maturation is in line with other life- history traits characterizing long-lived bats as K-strategists among small mammals.