Growth Rates and Age Estimation in Eptesicus fuscus and Comparison with Myotis lucifugus

Postnatal growth rates of free-living Eptesicus fuscus were determined by measuring length of forearm, length of the fourth metacarpal-phalangeal epiphyseal gap, and body weight of known-age juveniles. Linear segments of the forearm and epiphyseal gap curves yielded age-predictive regression equations with 95% confidence limits ranging from ±0.3 to 2.5 days and extending up to 43 days of age. Comparison of E. fuscus and Myotis lucifugus growth rates, when adjusted to body size, showed that E. fuscus grows at significantly slower relative rates than M. lucifugus. When litter size is accounted for, however, the rate of production of offspring biomass is relatively greater in E. fuscus.