Diurnal Body Weight Loss and Tolerance of Weight Loss in Five Species of Myotis

Dawn to dusk weight loss of Myotis leibii and M. yumnnensis, caged singly, and M. lucífugas, M. thysanodes, and M. velifer, caged singly and in groups of four, was determined in their natural roosting environments. Individual weight losses ranged from 6.4 to 21.9 per cent of initial body weight, whereas weight loss of grouped bats ranged from 9.9 to 16.2 per cent. Roosting conditions, temperature and relative humidity, are reflected in daily weight loss. Grouped M. thysanodes lost significantly less weight than individually caged bats. There was no difference in weight loss of individual and grouped M. lucífugas and M. velifer. Weight loss at which half of the individuals of each species except M. leibii died ranged from 22.8 to 32.3 per cent of initial body weight.