PHYSIOLOGICAL RESPONSES TO AMBIENT TEMPERATURE MANIPULATION BY THREE SPECIES OF BATS FROM ANDEAN CLOUD FORESTS

Abstract

´ridas, Universidad Nacional Experimental Francisco de Miranda, Apartado 7506 Coro, Venezuela (AA) In this paper we test the hypothesis that bats of the Andean highlands show distinctive metabolic responses compared with bats from lowland forests. We compared existing literature with new information on 3 bat species having the following food habits: a nectarivore (Anoura latidens), a frugivore (Sturnira erythromos), and an insectivore (Tadarida brasiliensis). Basal metabolic rate, as determined by oxygen consumption, thermal conductance, and body temperature were measured at ambient temperatures of 10‐38 8C. Some distinctive metabolic responses of these bat species, although varying with respect to food guild, allow us to separate them from counterpart species that are typically found in lowland forests. A. latidens is characterized by higher basal metabolic rate; however, thermal conductance and lower critical temperature values do not show an adaptation to cool environments, as expected. S. erythromos also increases its basal metabolic rate, but it maintains thermal conductance as expected, which implies a very important displacement of thermoneutral zone to lower temperatures. At temperatures below lower critical temperature, in addition to an endothermic response, S. erythromos sometimes expresses a hypothermic response or facultative torpor, independent of sex and body mass. T. brasiliensis has a lower basal metabolic rate and thermal conductance and also has its thermoneutral zone range displaced toward lower temperatures. Likewise, this species enters obligate torpor when ambient temperatures are below 22 8C.