Feeding ecology and diet

American leaf-nosed bats exhibit a wide variety of feeding habits and much of their morphological and behavioral diversity reflects adaptations for exploiting different kinds of food. The ancestral feeding mode in this family is undoubtedly insectivory, but blood-feeding was an early offshoot and nectarivory and frugivory are widespread in the family.

Foraging styles range from species that have small home ranges (many insectivorous or carnivorous phyllostomines and many frugivorous carolliinines and stenodermatines) to species with very large foraging ranges (the arid-zone glos-sophagine, Leptonycteris curasoae). Most phyllostomids commute only 0.6-1.2 mi (1-2 km) from their day roosts to feed, but individuals of L. curasoae sometimes commute up to 18.6 mi (30 km). Solitary foraging predominates in the family, but ries of long and short notes); these calls serve to reunite mother and baby in the roost after a female returns from foraging. Female harem-mates in Phyllostomus hastatus communicate while foraging with loud screeching calls. Certain stenodermatine bats (e.g., Artibeus jamaicensis and Uroderma bilobatum) produce intense warning calls that attract con-specifics or other species when they are captured in Japanese mist nets or while being handled.

Territorial behavior away from day roosts appears to be uncommon in phyllostomids bats. Male home ranges of the tent-roosting frugivore (Rhinophylla pumilio) do not overlap and are thought to be territories. The nectar-feeding bat (Glossophaga soricina) defends flowering stalks of agaves, at least in a suburban tropical setting, but no other evidence exists to suggest that flower-visiting or fruit-eating phyllosto-mids defend their food plants. Instead, it is common to see many individuals of several species feeding together in fruiting or flowering trees. The nectar bat (Leptonycteris curasoae) sometimes feeds in large numbers in isolated patches of flowering columnar cactus plants. Small groups of two to four bats of this species sometimes forage together at cactus and agave blossoms.

Because they live in tropical and subtropical habitats, phyl-lostomid bats do not hibernate and are active year-round. Al-

A California leaf-nosed bat (Macrotus californicus) showing its large ears. (Photo by Merlin D. Tuttle/Bat Conservation International/Photo Researchers, Inc. Reproduced by permission.)
White bats (Ectophylla alba) roost in a "tent" made from a heliconia leaf in a rainforest in Costa Rica. (Photo by © Michael & Patricia Fogden/Corbis. Reproduced by permission.)

group foraging also occurs. Mother-young pairs forage together in the common vampire (Desmodus rotundus); female harem-mates forage together in Phyllostomus hastatus; and adults (and possibly young) of L. curasoae and Phyllostomus discolor form small foraging groups when visiting flowers.

Fruit-eating phyllostomids typically harvest one fruit at a time and carry it to a night roost located 65.6-656 ft (20-200 m) from the fruiting plant to eat. As a result, substantial piles of fruit remains and seeds can accumulate under these roosts. When eating fruit, phyllostomids use two different feeding methods. Glossophagines, carolliinines, and species of Sturnira are rapid feeders; they consume the pulp and seeds of a fruit in one to three minutes and then harvest another fruit. They tend to feed on succulent fruit produced by early successional plants (e.g., Cecropia species and Muntingia calabura) and un-derstory shrubs (e.g., species of Piper, Solanum, and Vismia). In contrast, stenodermatines are slow feeders and carefully chew fruits into pellets while swallowing fruit juice and a small amount of pulp and seeds. They specialize on fig fruits, which contain high amounts of fiber, and other fruits produced by forest canopy trees.

Food sharing is known to occur in the carnivorous bat (Vampyrum spectrum); it also occurs in the common vampire.

Adult female vampires share blood meals with their young and with unrelated adult females in their roost. Blood-sharing among adults is thought to prevent individuals that have been unsuccessful in finding food on a particular night from starving. This form of food-sharing is one of the few examples of reciprocal altruism known to occur in non-primate mammals.

The feeding and foraging behavior of plant-visiting phyl-lostomids bats has considerable ecological and economic importance. Flower-visiting species, for example, are known to pollinate nearly 1,000 species of Neotropical plants, including trees, shrubs, vines, bromeliads, and arid-zone succulents such as columnar cacti and agaves. Economically important trees that are pollinated by these bats include balsa, kapok, and calabash, as well as agaves. Likewise, fruit-eating species disperse the seeds of hundreds of species of trees and shrubs. Important tree families containing bat-dispersed species include Anacardiaceae (cashew), Saptoaceae (chicle), Moraceae (figs), and Arecaceae (palms). Important understory plant families that are bat-dispersed include Piperaceae (pepper) and Solanaceae (nightshade). Bats such as Carollia perspicil-lata, Sturnira lilium, and Artibeus jamaicensis are very important for dispersing seeds to disturbed habitats where secondary plant succession and forest regeneration can begin.

A southern long-nosed bat (Leptonycteris curasoae) feeds on cactus fruit pulp. (Photo by Merlin D. Tuttle/Photo Researchers, Inc. Reproduced by permission.)

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