-Uaujr^necJ OCCASIONAL PAPERS MAY of the MUSEUM OF NATURAL HISTORY The University of Kansas Lawrence, Kansas NUMBER 36, PAGES 1-24 APRIL 16, 1975 POPULATION ECOLOGY OF THE GRAY BAT (MYOTIS GRISESCENS): FACTORS INFLUENCING EARLY GROWTH AND DEVELOPMENT Merlin D. Tuttle 1 Abstract Female Mijotis grisescens maintain high hody temperatures at maternity roosts throughout the period of lactation, even at low ambient temperatures (13.9 C C). The energetic cost of large differentials between body and ambient temperatures is greatly reduced by formation of large colonies, clustering be-havior, and choice of roost configurations that maximize retention of dissipated body heat. Growth rates of postnatal, preflight M. grisescens were studied at caves having a variety of ambient temperatures ( 13.9-26.3°C) and roost types, and numbers of young ranging from 600 to 22,100. Rates of weight gain varied from 0.20 to 0.39 gm/day and correlated best with the number of young bats present on a roost. Introduction Literature on the growth and development of bats is extensive; a partial listing includes studies under laboratory conditions (Orr, 1954; Jones, 1967; Kleiman, 1969; Kulzer, 1970; Maeda, 1972) as well as in the field (Pearson, Koford and Pearson, 1952; Davis, Bar-bour and Hassell, 1968; Davis, 1969; Dwyer, 1963, 1970; Kratky, 1970; Rakhmatulina, 1972; O'Farrell and Studier, 1973; Kunz, 1973, 1974). When growth rates between species have been compared, growth lias been treated as though it were constant for each species, with little consideration given to the influence of environmental variables. Although rates of growth and development are known to be con-elated with temperature (Eisentraut, 1937; Pearson, Koford and Pearson, 1952; Dwyer and Hamilton-Smith, 1965; Herreid, 1967; Kleiman, 1969; Racey, 1969; Orr, 1970), Kunz (1973, 1974) pro-vided the only major papers which report even the approximate l Museum of Natural History and Department of Svstematics and Ecology, The University ot Kansas, Lawrence, Kansas 66045.
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