Roosts used by maternity colonies of silver-haired bats in Northeastern Oregon

Abstract

Ten silver-haired bats (Lasionycteris noctivagans) that were pregnant or lactating were radiotracked to cavities in 17 trees. Twenty available trees containing cavities were randomly selected for comparison. I measured 19 characteristics of cavities, trees, and habitat in 0.1-ha plots centered on each tree. Increased insolation and retention of heat, which would particularly benefit maternity colonies, may have been achieved by roosts being high in trees and roost trees being farther from other tall trees and in earlier stages of decay. Protection of nonvolant young from terrestrial predators and newly volant young and adult females from aerial predators may have been provided by roosts located high in trees that retained hard wood and that were distant from trees that could restrict flight to and from the roost. Roost trees were taller, retained more of their tops, and more often protruded above the canopy than available trees, making them conspicuous in the auditory and visual landscape.