Reproductive success, colony size and roost temperature in attic-dwelling bat Myotis myotis

Some cave-dwelling bat species such as Myotis myotis now also roost in buil dings in parts of their range. I studied the effects of roost temperature a nd colony size on reproductive success of colonies of M. myotis located in buildings. Temperatures in attics fluctuated considerably and altered the t hermal conditions at the roost during the breeding season. Inter-colony var iation was recorded with respect to factors indicating reproductive success (number, growth, and mortality of juveniles until fledging). However, over -winter survival varied more between years than between colonies. Colony si ze did not influence development or mortality of juveniles. High average ro ost temperatures favoured development of juveniles but did not influence mo rtality. Unlike the situation in caves, large colony sizes are not advantag eous in buildings.