Behavioral Character Displacement: Evidence of Food Partitioning in Insectivorous Bats

Abstract

Two extremely similar insectivorous bats, Myotis evotis and M. auriculas, differ in food preferences when sympatric (Black, 1974). Myotis auriculus preys generally upon moths and some beetles, whereas M. evotis specializes on beetles. Does this specialization of M. evotis persist in allopatry, indicating that it has evolved as a food specialist, or in the absence of its close competitor, does it eat both moths and beetles without a strong preference? What sort of effect, if any, does M. evotis exert on the diet of M. auriculus in areas of sympatry? Both species were captured in areas of allopatry during the summer of 1972. Fecal samples were collected and analyzed using Black's (1974) technique. My results indicate that when in allopatry, M. evotis and M. auriculus have similar food habits. Thus, in sympatry, competition for food is avoided by changes in food preferences of M. evotis. Furthermore, each species exhibits sexual differences in foods taken in areas of allopatry, indicating that intraspecific niche subdivision occurs in each of these bats only in the absence of the potential competitor.