Meeting Abstract

108.3  Tuesday, Jan. 7 08:45  Energetic costs of pregnancy for small bats at high latitudes BOYLES, J.G.*; JOOSTE, E.; RUTHERFORD, R.W.; MCCRACKEN, G.F.; Southern Illinois University; Southern Illinois University; Slana, AK; University of Tennesee jgboyles@siu.edu

Small endotherms at high latitudes may experience unique bioenergetic constraints during the reproductive season because of cool temperatures and short summers. Insectivorous bats may be under even more severe constraints than other endotherms because of their unique life history traits, including nocturnality. We estimated an energy budget for pregnant little brown bats (Myotis lucifugus) in an anthropogenic roost in eastern Alaska (~63°N) using temperature-sensitive radio-transmitters in the field, metabolic rate measurements in the lab, dietary analysis of fecal samples, and energetic content estimates of likely prey items. Body temperature patterns varied widely with some individuals maintaining homeothermy while other individuals commonly entered torpor, a pattern that is thought to be relatively rare among pregnant insectivorous bats. Our estimate of average daily energy expenditure (DEE) for bats that remained euthermic was identical to previous DEE estimates for little brown bats in New Hampshire, where energetic constraints are presumably less severe. However, as expected, torpor resulted in considerable energy savings, which may help some individuals at high latitudes weather the high cost of pregnancy, even with relatively short foraging periods associated with the lack of true darkness. Bats in this study almost completely avoided eating the ubiquitous mosquitoes, which we found to have very little energetic value. Instead, they consumed large numbers of spiders and moths, both of which are relatively energy rich. Thus it seems that relatively minor physiological (e.g., increased torpor usage) and behavioral (e.g., slight dietary shifts) adjustments are sufficient for bats to survive and reproduce at high latitudes.