Growth rate and development in infant Natterer's bats (Myotis nattereri) reared in a flight room

Myotis nattereri born and reared by their mothers in a flight room had a mean birth body mass of 3.4 ga and forearm length of 17.00 nun. Infants opened their eyes at 6 days old, and they were no longer always found roosting attached to their mothers after this age. They were fully furred at 7-8 days and began to flap their wings at 15 days. Growth was initially rapid and linear until 20 days of age and then slowed. At 58-60 days, mean body mass was 8.8 a (89% of adult mass) and mean forearm length was 40.55 nun (98% of adult length). Juveniles began to fly at 20 days, at which age their forearm length was 93.4% of mean adult value. Forearm data were best fitted by the logistic growth model (k = 0.18; asymptotic length = 40.79 mm for males) and body mass data by the von Bertalanffy equation (k = 0.10; asymptotic mass = 8.42 g for males). Pre-flight growth and development rates were similar to those in other British vespertilionid bats, but M. nattereri showed very rapid development of foraging ability after they began to fly. Mothers suckled only their own infants and transported flightless young between roost boxes, on average every 5.3 days.