JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. American Society of Mammalogists is collaborating with JSTOR to digitize, preserve and extend access to Journal of Mammalogy.ABSTRACT.-A study was made of the nightly activities of four species of mormoopid bats (Pteronotus pamellii, P. personatus, P. davyi, and Mormoops megalophylla) that inhabited a cavern system in the Sierra Madre Occidental in Sinaloa, Mexico. The bats were observed, were mist-netted along heavily traveled flyways, and recaptures of previously marked individuals were recorded. Activity of bats began shortly after sunset and there was considerable light-testing prior to emergence. Some bats began returning to the roost as early as 1.5 hours after the exodus flight began, but most bats appeared to remain away from the roost for from 5 to 7 hours. The congestion just before dawn when masses of returning bats attempted to re-enter the roost suggested that size of the colony may have been limited by size of the roost entrance. Regarding evening dispersal flights: flyways to foraging grounds were long (to at least 3.5 kilometers but almost certainly several times this length for some individuals); bats sometimes used shortcuts along dispersal routes, but normally followed topographic features; in some cases there appeared to be distinct spatial separation between the flyways of different species; individuals showed some fidelity to particular flyways; and natural environmental stimuli may have caused abandonment of regularly used flyways. We estimated that the 400,000 to 800,000 bats comprising the large colony consumed from 1902 to 3805 kilograms of insects each night. Thus, these bats are of considerable significance in the energy flow of tropical ecosystems.
Relatively little is knownregarding the nightly behavior of bats. Most are small and nocturnal and, consequently, difficult to observe closely when active. Vaughan (1959) recorded observations of foraging of species of Macrotus, Myotis, and Eumops. Hall and Dalquest (1963) and Villa-R. (1966) described general activities of neotropical bats representing several families and, more recently, Goodwin (1970) gave information on habitat preferences, roosting behavior, and relative abundance of several Jamaican mormoopids. The important recent findings of several authors (including Dwyer, 1971; Nelson, 1965; and Wickler and Uhrig, 1969) regarding complex social behavior of various species of bats indicate that field studies will continue to reveal basic knowledge of their biology.Here we discuss the nocturnal activities of four species of mormoopids inhabiting a single large cavern near the small mining village of Panuco in Sinaloa, Mexico. The four species-Pteronotus parnellii, P. personatus, P. davyi, and Mormo...