Terry A. Vaughan

Nocturnal Behavior of the African False Vampire Bat (Cardioderma cor)

Nocturnal behavior of the African false vampire bat ( Cardioderma cor ) was studied in bushland in southern Kenya, East Africa. Observations were made with a night-viewing device, and work was concentrated on the foraging strategy. This bat roosts in hollow baobab trees in groups of up to some 80 individuals. At night each bat occupies an exclusive foraging area. Individuals spend considerable time singing and establishing their exclusive areas during the March–April wet season when food is abundant; these areas have greatest survival value toward the end of the long May–October dry season, when food is in short supply, foraging occupies nearly the entire night, and singing is infrequent. Nocturnal time budget is characterized by long periods spent perching in low vegetation and listening for terrestrial prey. Flights to capture prey and between perches are brief and short, usually lasting less than 5 seconds and covering less than 25 meters. Food is typically captured on the ground, and consists primarily of large, ground-dwelling beetles, but centipedes and scorpions, and on rare occasions small bats, are also taken. During parts of the rainy seasons leaf gleaning and aerial captures of insects are important; at these times katydids (Tettigoniidae), locusts (Locustidae), and sphinx moths (Sphingidae) are major food items. Pronounced seasonal shifts in foraging behavior associated with the bimodal pattern of rainfall are discussed, and the evolution of the bats unusual style of foraging is considered.

Roosting Ecology of the Pallid Bat, Antrozous pallidus

Daytime roosting behavior of pallid bats ( Antrozous pallidus ) was studied in central Arizona. Bats were present in the area from March or April until November and roosted in cliffs in colonies generally including 20 or more individuals. Pallid bats were highly selective in their choice of roost sites and minimized diurnal energy output by adaptive hypothermia and behavioral thermoregulation. In spring and autumn the bats roosted in vertical crevices responsive to changes in ambient temperatures. Here temperatures remained low and the bats were torpid for much of the day, but when the crevices became heated in the late afternoon the bats were passively warmed prior to emergence. Deep, horizontal crevices were preferred in summer; cliffs function as massive heat sinks, and in summer crevice temperatures remained moderate and relatively stable. Throughout most of the day both the deep parts of the crevices and the body temperatures of the bats remained close to 30°C; at this body temperature pallid bats have unexpectedly low metabolic rates (Trune, 1974). By adjusting their positions and closeness to other bats in the thermal gradient within the crevice, bats dissipate heat early in the day, maintain a low metabolic rate through most of the day and elevate the body temperature prior to emergence in the evening. Of vital importance to pallid bats in the summer are social behaviors that promote communal roosting at “traditional” crevices.

Nocturnal and Seasonal Activities of the Pallid Bat, Antrozous Pallidus

Nocturnal and seasonal activities of pallid bats ( Antrozous pallidus ) were observed in central Arizona. The pallid bat night is characterized by two foraging periods with an intervening period of night roosting. Foraging pallid bats have a characteristic style of flight well suited to the taking of relatively large, substrate-roving or slow flying prey. After the initial foraging period pallid bats locate one another through vocal communication and gather in night roosting clusters where they enter torpor. Durations and scheduling of nocturnal activities vary seasonally. Cool months are characterized by smaller colonies of bats, greater fidelity to certain colony sites, slower and later emergence, briefer foraging periods and longer periods of night roosting. Up to 75 percent of the time spent away from diurnal retreats is devoted to night roosting in the autumn. Young are born in June, and during most of the summer adult males do not seem to occur sympatrically with females and young. Females and young appear to forage together in July and August, when little fidelity is shown to roosting sites, large colonies exist, emergence is faster and earlier, and more time is spent in foraging than in cooler months. In mid-August a postbreeding dispersal occurs. These activities and behaviors are discussed in terms of the energetic demands on the bats and the socialization of young.

Morphology and Flight Characteristics of Molossid Bats

Selected aspects of the morphology of bats of the family Molossidae are described and the functional significance of these features are discussed. The structure and proportions of the ears and the wings are considered to reflect primarily the rapid enduring flight typical of molossids. Comparisons of some characteristics of the wings of three molossids and of four bats of the family Vespertilionidae were made, and several aerodynamic relationships were applied to a consideration of the styles and speeds of flight of these bats. Molossid bats in general seem adapted to fast flight in open areas, whereas the vespertilionids studied are apparently suited to slower flight fairly low to the ground, near vegetation and other obstacles.

Nightly Activities of Mormoopid Bats

A study was made of the nightly activities of four species of mormoopid bats ( Pteronotus parnellii, 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.

Ecological observations on an East-African bat community

The stricture and ecology of bat faunas is a subject of interest to mammalogists (Findley, 1976; Wilson, 1973). Syntopic African bat communities, however, have received little study in comparison with neotropical faunas (cf. Fleming et al., 1972 ; LaVal and Fitch, 1977; McNab, 1971). Verschuren (1957) presented natural history information and species accounts for a localized central African bat fauna. Foraging related characteristics of a Rhodesian community have also been analyzed (Fenton, 1975; Fenton et al., 1977), but not on a seasonal basis. Other reports on African bat faunas are restricted to regional summaries (cf. Koopman, 1975 or Rosevear, 1965) and do not consider ecological aspects of a single localized community. The purpose of our study was to follow species composition, reproduction, and foraging related characteristics of an East African bat fauna over a full annual cycle.

Seasonality and the Behavior of the African Yellow-Winged Bat

The African yellow-winged bat ( Lavia frons ) was observed in Kenya, East Africa, through one wet and one dry season (December 1982 to July 1983). This opportunistic, sit-and-wait predator typically forages from the crowns of Acacia tortilis and captures insects through a broad range of elevations by brief, precise interceptions. Lavia is monogamous. Members of a pair roost together in a territory defended by the male, forage either separately or together, and share the territory for some 3 months with the single young. Acacia tortilis responds to erratic dry-season rains by flowering and growing new leaves; attending brief bursts of insect abundance may be of crucial importance to Lavia during dry-season energy bottlenecks. Many of the most distinctive aspects of the life history of Lavia —monogamy, territoriality, the division of labor, opportunistic foraging, a long mother-young association, and a close association between Lavia and A. tortilis —probably are adaptations to recurring periods of energy stress.

Movements Made by Two Species of Pocket Gophers

Information is presented on dispersal movements made by valley pocket gophers, Thomomys bottae, and northern pocket gophers, T. talpoides, introduced into areas with which the animals were unfamiliar. Most long movements were made under snow cover. Thomomys talpoides dispersed from introduction sites more frequently and moved greater distances than did T. bottae. The mean distance moved by T. talpoides in one year was 785 feet, and the longest movement was 2590 feet. Comparable figures for T. bottae are 198 feet and 900 feet. The differences in dispersal abilities or tendencies between the species are probably basic behavioral distinctions which may be related to the differences in the environments occupied by the animals. Little information is available on movements made by pocket gophers under natural conditions. Bryant (1913), Howell (1922), and Imler (1945) reported on surface movements of pocket gophers, and Howard and Childs (1959) recorded distances 14 prebreeding individuals traveled. In the present study, distances moved by transplanted individuals of two closely related species of pocket gophers were recorded. On the basis of these records, the abilities or tendencies of the animals to disperse are compared and discussed. The study area was approximately six miles north of Cotopaxi, Fremont Co., Colorado, at roughly 7500 feet elevation. The locality is mountainous and rocky, and is characterized by pinyon pine, Pinus edulis, juniper, Juniperus scopulorum, ponderosa pine, Pinus ponderosa, Gambel oak, Quercus gambellii, and mountain mahogany, Cercocarpus montanus. The ground cover of the areas occupied by pocket gophers is dominated by blue grama, Bouteloua gracilis, and sleepygrass, Stipa robusta. Other conspicuous plants are rabbitbrush, Chrysothamnus nauseosus, summer-cypress, Kochia scoparia, and western beeplant, Cleome serrulata. Acknowledgments.-Thisstudy was supported by National Science Foundation Grant G-9807. I would like to express my appreciation for critically reading the manuscript to Paul H. Baldwin, Department of Zoology, Colorado State University; Richard M. Hansen, Colorado State University, Agricultural Experiment Station; and Ronald A. Ryder, Department of Forest Recreation and Wildlife Management, Colorado State University. For assistance with field work I wish to thank Roger E. Baker, Keith E. Evans, LeMoyne B. Marlatt, Gary T. Myers, and Ronald L. Perry.

Food Habits of the Plains Pocket Gopher in Eastern Colorado

The contents of the stomachs of 298 Geomys bursarius taken in the sandhills of eastern Colorado were examined microscopically. As a basis for judging food preferences, floral composition estimates were made at each capture site. Approximately 64% of the yearly diet was grass, although forbs were preferred when they were succulent in spring and summer. The plants most commonly eaten by pocket gophers and the percentages of the yearly diet they comprised were: Stipa comata , 22%; Agropyron smithii , 14%; Bouteloua gracilis , 12% and Opuntia humifusa , 9%. The four most highly preferred plants and their preference indices were: Opuntia humifusa (25.0); Astragalus spp. (10.0); Stipa comata (5.5) and Sphaeralcea coccinea (5.0). Aboveground parts of plants (leaves and stems) were most important in the diet in July, and least important in February and made up 26% of the yearly diet. The food habits of the different sex and age-classes differed slightly. Young animals ate significantly more aboveground vegetation than did adults, and young and adults had different preferences for certain plants.

Resource Allocation in Some Sympatric, Subalpine Rodents

The diets and foraging patterns of four sympatric rodents ( Eutamias minimus, Thomomys talpoides, Peromyscus maniculatus , and Microtus montanus ) were studied for three summers in subalpine meadows in northern Colorado. The rodents were taken in half-acre quadrats isolated by electric fences, and the diets were determined by microscopic examinations of stomach contents. Records of times of capture and frequency data on the plants at capture sites contributed to an evaluation of feeding biology. Each species utilized a different feeding strategy; the species with broadly similar diets had contrasting specific food-item preferences and were spatially or temporally separated during foraging. Thomomys talpoides and M. montanus were both entirely herbivorous, but each preferred different plants and different size classes of plants, and they foraged in different microenvironments. Both E. minimus and P. maniculatus ate primarily seeds and arthropods, but they preferred different kinds of seeds and depended on arthropods to differing degrees; E. minimus was diurnal and P. maniculatus was nocturnal. Feeding niche displacement between the rodents was especially striking during spring snowmelt and after late summer frosts, times when food was in short supply. The striking changes in the diets of the rodents during the summer and relationships between diets and feeding-activity rhythms are discussed.