Summer habitat use and response to food patches by insectivorous bats in a desert community

Habitat use by an Arizona insectivorous bat community was examined using ultrasonic sensing equipment which allowed identification of bat species in the field by their echolocation calls. Response to prey patchiness by these species was tested using ultraviolet lights to attract swarms of insects. , All species of bats regularly observed were found in each of the 3 habitats examined. Total bat numbers were greater in forest than in open desert or scrub, but the open habitats had more even species distributions resulting in higher species diversity. Bat activity in all habitats continued throughout the night. Peaks in nightly activity in the scrub and desert typically occcurred after midnight, while in the canon forest activity was highest in the early evening, suggesting a movement of bats from the canons into the other habitats during the course of the night. Activity was not suppressed by light rain, wind or moonlight, nor was activity correlated with temperature or humidity. All species of bats examined responded to light-induced prey patches on at least some occasions. Some species appeared to be positively associated with others, while no instances of negative association or agonistic behaviour were noted. These data indicate a bat community in which the species are highly adapted to patchy prey distributions. Prey did not appear to be limiting and the transient, dynamic nature of the bat community and high degree of association between species suggest a lack of interspecific competition during the summer. A "patchwork community" of non-competing, independently population-limited species is hypothesized.