American Leaf-Nosed Bats (Phyllostomidae)

(Phyllostomidae)

Class: Mammalia

Order: Chiroptera

Suborder: Microchiroptera

Family: Phyllostomidae

Thumbnail description
Small to relatively large bats, most of which have a fleshy, triangular nose-leaf projecting above the nostrils

Size
Head and body length 1.6–5.3 in (40–135 mm); tail 0–2.2 in (0–55 mm); forearm 1.2–4.1 in (31–105 mm); weight 0.2–6.8 oz (5–190 g)

Number of genera, species
49 genera; 151 species

Habitat
Mainly forests, but also deserts

Conservation status
Extinct: 1 species; Endangered: 4 species; Vulnerable: 25 species; Lower Risk/Near Threatened: 36 species; Data Deficient: 5 species

Distribution
Subtropical and tropical America from southern Arizona and the West Indies to northern Argentina

Evolution and systematics

Members of this family are among the most common mammals in American tropical forests. Rainforests in Central and South America contain 31–49 species of phyllostomids; tropical forests receiving less rainfall contain 20–30 species; and dry regions contain two to three species. In addition to being one of the most taxonomically diverse families of bats, the Phyllostomidae is the most ecologically diverse group of bats. Food habits range from insects, flowers, and fruit to blood and other vertebrates. Sizes of social groups range from monogamous pairs to colonies containing several hundred thousand individuals.

Along with the two small American families, Noctilionidae (one genus, two species) and Mormoopidae (two genera, eight species), the Phyllostomidae is classified in superfamily Noctilionoidea of suborder Microchiroptera. Food habits of noctilionids (also known as bulldog bats) include insects and fish, while mormoopids (also known as moustached or leaf-chinned bats) are insectivorous. These two families are unknown in the fossil record other than from Pleistocene deposits. The earliest known fossil, phyllostomid (Notonycteris), comes from the Miocene of Colombia (about 20 million years ago). It is likely that each of these families evolved in South America. All three families occur in the West Indies as well as in mainland subtropical and tropical America.

Reflecting its substantial dietary diversity, the Phyllostomidae is currently classified into eight subfamilies containing a total of 49 genera and 151 species. Subfamilies and their diversity include: Phyllostominae (11 genera, 37 species), Lonchophyllinae (3, 9), Brachyphyllinae (1, 2), Phyllonycterinae (2, 4), Glossophaginae (10, 23), Carolliinae (2, 7), Stenodermatinae (17, 66), and Desmodontinae (3, 3). Phyllostomines include insectivores and carnivores; lonchophyllines, phyllonycterines (a West Indian group), and glossophagines are nectarivores; brachyphyllines (a West Indian group), carolliinines, and stenodermatines are frugivores; and desmodontines are blood-feeding vampires.

Physical characteristics

Sizes and facial characteristics of American leaf-nosed bats differ substantially among the subfamilies and reflect their diverse feeding adaptations. Phyllostomines include the largest members of the family (3.2–6.7 oz; 90–190 g) and generally have the longest nose leaves. The nose leaf of the sword-nosed bat (Lonchorhina aurita), for example, is as long as its long, pointed ears. Large members of this subfamily have robust canines and molars for killing and chewing vertebrate prey. At the other end of the size spectrum are flower-visiting bats (Lonchophyllinae and Glossophaginae), which weigh 0.2–0.8 oz (7–25 g). These bats have elongated muzzles, small nose-leaves, long tongues, and dentition that are reduced in size and number. Fruit-eating bats (Stenodermatinae) weigh 0.2–2.8 oz (5–80 g), have medium-sized nose leaves, and generally have flattened faces with dagger-like canines and broad cheek teeth for grabbing and crushing fruit. Vampire bats (Desmodontinae) weigh 0.2–1.7 oz (20–50 g) and have much-reduced nose leaves and a reduced number of morphologically specialized teeth. The two upper incisors are sharp and chisel-like for making incisions in the skin of mammals or birds.

The fur color of phyllostomid bats is generally brown or gray, but one species (Ectophylla alba) is white. Many genera of stenodermatines, which often roost in foliage by day, have white facial stripes, and a few have a white mid-dorsal stripe.

The nose-leaves that give this family its common name are also found in several families of Old World Microchiroptera (e.g., Nycteridae, Rhinolophidae, Hipposideridae, and Megadermatidae). All of these bats emit echolocation sounds through their nostrils rather than through their mouths. It is thought that these structures serve as an acoustic lens that focuses the outgoing sound into a narrow beam.

Distribution

Phyllostomid bats are currently distributed from the southwestern United States and the West Indies south to northern Argentina and central Chile. Two subfamilies (Phyllonycterinae and Brachyphyllinae) are restricted to the West Indies, which generally lack members of the Phyllostominae and Carolliinae. Lonchophyllinae and Desmodontinae are absent from the West Indies, although the common vampire, Desmodus rotundus (Desmodontinae), is known as a fossil from Cuba. In the late Pleistocene, vampire bats had a much broader distribution and occurred across the southern United States. Highest diversities of phyllostomid bats, in terms of number of subfamilies and species, occur in the lowland rain-forests of northwestern South America and adjacent Central America. Phyllostomid diversity declines with altitude, latitude, and increasing aridity.

Habitat

Most phyllostomid bats are forest-dwellers. They live in a wide range of forest habitats, including tropical rainforests, tropical dry forests, and subtropical cloud forests. A few species, including two species of Leptonycteris and Choeronycteris mexicana (Glossophaginae) in Mexico and Platalina genovensium (Lonchophyllinae) in Peru, inhabit deserts or very dry tropical forests where they are important pollinators of columnar cacti and century plants (agaves).

Daytime roost structures of American leaf-nosed bats are quite diverse. Most species live in caves and/or hollow trees, but alternate roosts include mines, culverts, hollow logs, under tree roots, undercut river banks, houses, abandoned termite nests, and tree foliage. Suitable roosts are extremely important in the ecology of these bats and can sometimes limit their abundance and distribution. The relatively recent local extinction of many species of mormoopid and phyllostomid bats in the West Indies, for example, was likely caused by the inundation of extensive cave systems as a result of post-Pleistocene increases in sea level.

In addition to providing protection from inclement weather and predators, cave roosts provide stable microclimates. Most cave-dwelling phyllostomids live in roosts that are at or slightly below outside ambient temperatures. These temperatures are often below the thermoneutral zones of the bats, which forces them to expend energy to maintain a constant, high body temperature (98.6–100.4°F; 37–38°C). Certain glossophagine bats, however, including Leptonycteris curasoae and Monophyllus redmani, live in hot, humid caves where temperatures reach 91°F (33°C) within their thermoneutral zones. These caves are hot because they trap the body heat of tens of thousands of phyllostomid and mormoopid bats. In addition to reducing individual daily energy costs and rates of evaporative water loss, this roosting strategy increases the developmental rates of embryos and lactating babies.

Most members of the Stenodermatinae usually roost either solitarily or in small groups in foliage and, hence, are constantly exposed to (shaded) ambient temperatures. In addition, several species (e.g., Uroderma bilobatum, Artibeus watsoni, and Ectophylla alba) are known to construct "tents" by clipping the leaves of banana-like herbs, philodendrons, and palms to form shelters from rain and predators. Species of Rhinophylla (Carolliinae) also use tents as day roosts. Tent roosts are short-lived, which forces groups of bats to constantly change roost sites.

Behavior

Most phyllostomid bats are colonial rather than solitary roosters, but roost size varies tremendously within and between species. Modal roost sizes within most species are relatively small and range from a few individuals to a few thousand individuals. A few species (the hot cave bats), in contrast, are highly colonial and roost in groups of tens of thousands to several hundred thousand individuals. Except for the flower-visiting, hot-cave bats, there does not appear to be a strong correlation between feeding habits and average roosting group size in this family. Vampires, fruit-eaters, many flower visitors, and certain carnivore/omnivores (e.g., Phyllostomus hastatus) sometimes live in roosts containing thousands of individuals. Small roost groups occur in pure carnivores, insectivorous phyllostomines, and a variety of flower-visiting and fruit-eating species (especially the tent-making stenodermatines).

Seasonal sexual segregation commonly occurs in many bats, including phyllostomids. Segregation usually involves the formation of maternity roosts by females. This behavior is most strongly developed in migratory glossophagines such as Leptonycteris curasoae, in which females sometimes form maternity roosts containing tens of thousands of adults. Single-sex maternity roosts also occur in non-migratory glossophagines and members of other subfamilies.

Like other Microchiroptera, phyllostomids use ultrasonic sounds for foraging and communication. Unlike other microbats, however, most phyllostomids produce very low intensity sounds that contain only about one-thousandth the sound energy as similar-sized vespertilionid bats. Additional characteristics of their echolocation sounds include multiple harmonics, frequency modulation, and short duration. These sounds provide short-range (3.2–6.5 ft; 1–2 m) information about potential insect or other prey items in areas of high vegetation clutter. In addition to echolocation information, many phyllostomids use other sensory modes (e.g., vision such as the ground-feeding insectivore, Macrotus californicus, and many flower-visiting bats, or olfaction such as many fruit-eating bats) to find food. Certain phyllostomines, for example, locate prey using prey-generated sounds (e.g., singing katydids, Tonatia sylvicola, and singing male frogs, Trachops cirrhosus). Careful experiments have shown that plant-visiting phyllostomids use a combination of vision, olfaction, and echolocation to locate and gain access to their food.

Echolocation and other kinds of vocalizations are also used for communication in these bats. Babies communicate with their mothers using "double-note" calls (rapidly repeated series 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 conspecifics 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 phyllostomids 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, phyllostomid bats do not hibernate and are active year-round. Although most species are sedentary and do not migrate among habitats during the year, a few species are known to undergo seasonal migrations. Relatively short-distance (<62 mi; 100 km) altitudinal movements are known to occur in three Mexican or Central American species—two frugivores, Carollia perspicillata and Sturnira lilium, and the nectar bat, Leptonycteris curasoae. Longer distance latitudinal migrations occur in three arid-zone nectar bats: Leptonycteris curasoae, L. nivalis, and Choeronycteris mexicana. Movements of over 620 mi (1,000 km) occur in females of L. curasoae as they move between spring maternity roosts in the Sonoran Desert and their late fall mating sites in west central Mexico. The lonchophylline nectar bat (Platalina genovensium) is also thought to undergo substantial migrations in the Andes of Peru.

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 glossophagine, 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 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 (20–200m) 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 understory 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 phyllostomids 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 perspicillata, Sturnira lilium, and Artibeus jamaicensis are very important for dispersing seeds to disturbed habitats where secondary plant succession and forest regeneration can begin.

Reproductive biology

In part, roosting group size reflects the mating systems of American leaf-nosed bats. At one extreme is the carnivore Vampyrum spectrum, which roosts in small family groups consisting of a pair of adults and up to three of their recent offspring. This species has a monogamous mating system, the only known example so far in this family, and adults share the prey they capture with each other and their offspring. It would not be surprising to learn that other carnivorous species (e.g., Chrotopterus auritus) are also monogamous. At the other extreme are colonially roosting species with harem polygynous mating systems, the most common mating system in this family. In these systems, single males aggressively defend groups of females against the intrusions of other males. Only a fraction (about 20% in Carollia perspicillata) of adult males possesses a harem at any given time; the majority of adult males are bachelors. Harems either form seasonally or remain stable in their female composition year-round. The most stable harems occur in the greater spear-nosed bat (Phyllostomus hastatus), in which groups of unrelated females may spend their entire adult lives together. More ephemeral groups of females occur in two common fruit-eating species, Carollia perspicillata and Artibeus jamaicensis. Genetic studies indicate that harem males father most, but not all, of the babies born in their harem.

Another variation on the theme of polygyny in phyllostomids is the multiple-male/multiple-female group. An example of this mating system occurs in the common vampire, Desmodus rotundus. In this species, stable groups of eight to 12 adult females live together in roosts with several adult males, which form a dominance hierarchy regarding mating rights. When roosting in hollow trees, males fight with each other for access to the top of the roost, where most matings take place. In the phyllostomine (Macrotus californicus), seasonal aggregations of adult males and females form in which males defend preferred roosting sites against other males. They attract females for mating with wing flapping and vocalization displays.

Like all bats, American leaf-nosed bats are low-fecundity animals. Females almost always give birth to a single young once or twice a year. Insectivorous or carnivorous species and vampires tend to be monestrous and undergo a single pregnancy each year. Most plant-visiting species, in contrast, are polyestrous and undergo two pregnancies a year. In Central America, one birth occurs in the late dry season (March–April) and another occurs in the middle of the wet season (July–August) in these species. Gestation periods are relatively long and last about four months in carolliinines and many stenodermatines. It lasts about seven months in the common vampire. In at least two species, Macrotus californicus and Artibeus jamaicensis, gestation is prolonged as a result of delayed embryonic development.

The timing of reproduction in the glossophagine (Leptonycteris curasoae) shows interesting intraspecific variation. Its general pattern is monestry, but the timing of births varies geographically. In northern South America and northern Mexico, births occur in May after a five-to-six-month gestation period. In southern Mexico, births occur in December after a similar gestation period. May births coincide with the flowering seasons of columnar cacti in the Sonoran Desert of northern Mexico and in the arid regions of northern South America. December births in southern Mexico coincide with the flowering seasons of tropical dry forest trees and shrubs. In Mexico, most of the mating activity that produces these babies occurs in caves located in south central Mexico, far from the maternity sites. After mating, females migrate north (in the spring) or south (in the fall) to form maternity colonies. Genetic studies indicate that populations belonging to these reproductive demes currently undergo substantial gene flow. Different reproductive schedules have not resulted in genetic isolation in this species in Mexico.

With a few notable exceptions, parental care is not extensive in this family. Most young phyllostomids are weaned about six weeks after birth, and few young have any further contact with their mothers (or fathers). Extended parent-offspring contact occurs in at least two species, the spectral (Vampyrum spectrum) and the common vampire (Desmodus rotundus). In the former species, young bats remain with their parents long after weaning and are provisioned with vertebrate prey while they are learning to hunt for themselves. Young vampires remain with their mothers for up to a year after birth. Their mothers sometimes feed them regurgitated blood after they reach three months of age, and they continue to forage with their mothers until they are one year old.

Conservation status

In terms of relative abundance, American leaf-nosed bats range from rare to very common. Rarity or commonness in these bats is mostly associated with their food habits or trophic position. As expected, carnivores such as Vampyrum spectrum are rare. Insectivorous phyllostomines in general are also far less common in any habitat than frugivorous carolliinines or stenodermatines. Flower visitors tend to be substantially less common than fruit-eaters. The local abundance of common vampires varies tremendously and is correlated with the availability of domestic animals. In primary forest, vampires are uncommon, but they can be very common in disturbed habitats whenever they have regular access to livestock.

In 2001, the IUCN/SSC Chiroptera Specialist Group listed four species of phyllostomids as Endangered and 25 species as Vulnerable. The endangered species included Phyllonycteris aphylla on Jamaica, Chiroderma improvisum on Guadeloupe and Montserrat, and Sturnira thomasi on Guadeloupe, as well as Leptonycteris nivalis in Mexico. The vulnerable species included seven phyllostomines, five lonchophyllines, four glossophagines, and nine stenodermatines. Only two of these species, Ariteus flavescens and Stenoderma rufum, occur on islands.

Phyllostomid bats, and Latin American bats in general, suffer from the "vampire problem," meaning most Latin Americans consider all bats to be vampiros that should be destroyed. Millions of cave-dwelling bats in Mexico alone have been killed in recent decades as a result of misguided vampire-control programs. Until enlightened vampire-control methods become widespread in Latin America, all colonially roosting bats are vulnerable to local destruction. Bat Conservation International, located in Austin, Texas, United States, has made a major effort to disseminate information about the selective control of vampires in areas where they pose an economic threat in Latin America.

Significance to humans

Because it sometimes transmits rabies to livestock, the common vampire is the most notorious phyllostomid bat. It has been estimated that 100,000 or more cattle die annually, at a cost of $40 million, as a result of vampire-transmitted rabies in Latin America. On the other hand, other phyllostomid bats can have an important positive impact on humans through their pollination and seed dispersal activities. Many of the market fruits in both the New and Old World tropics are bat-dispersed species. Sisal and tequila plants originally relied on phyllostomids bats for their pollination. Forest regeneration resulting from seed dispersal and enhanced fruit and seed set resulting from pollination are two of the beneficial ecosystem services provided by phyllostomid bats.

Species accounts

Resources

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Dobat, K. Bluten and Fledermause. Frankfurt am Main: Dr. Waldemar Kramer, 1985.

Fleming, T. H. The Short-tailed Fruit Bat. Chicago: University of Chicago Press, 1988.

Fleming, T. H., and J. Nassar. "Population Biology of the Lesser Long-nosed Bat (Leptonycteris curasoae) in Mexico and Northern South America." In Columnar Cacti and Their Mutualists, edited by T. H. Fleming and A. Valiente-Banuet. Tucson: University of Arizona Press, 2002.

Greenhall, A. M., and U. Schmidt, eds. Natural History of Vampire Bats. Boca Raton: CRC Press, 1988.

Heideman, P. D. "Environmental Regulation of Reproduction." In Reproductive Biology of Bats, edited by E. G. Crichton and P. H. Krutzsch. San Diego: Academic Press, 2000.

McCracken, G. F., and G. S. Wilkinson. "Bat Mating Systems." In Reproductive Biology of Bats, edited by E. G. Crichton and P. H. Krutzsch. San Diego: Academic Press, 2000.

Nowak, R. M. Walker's Bats of the World. Baltimore: Johns Hopkins University Press, 1994.

Wilkinson, G. S. "Information Transfer in Bats." In Ecology, Evolution and Behaviour of Bats, edited by P. A. Racey and S. M. Swift. Oxford: Clarendon Press, 1995.

Handley Jr., C. O., D. E. Wilson, and A. L. Gardner, eds. "Demography and Natural History of the Common Fruit Bat, Artibeus jamaicensis, on Barro Colorado Island, Panama." Smithsonian Contributions to Zoology 511 (1991).

Simmons, N. B., and R. S. Voss. "The Mammals of Paracou, French Guiana: A Neotropical Lowland Rainforest Fauna, Part 1. Bats." Bulletin of the American Museum of Natural History 237 (1998).

Wetterer, A. L., M. V. Rockman, and N. B. Simmons. "Phylogeny of Phyllostomid Bats (Mammalia: Chiroptera): Data From Diverse Morphological Systems, Sex Chromosomes, and Restriction Sites." Bulletin of the American Museum of Natural History 248 (2000).

Bat Conservation International. P.O. Box 162603, Austin, TX 78716 USA. Phone: (512) 327-9721. Fax: (512) 327-9724. E-mail: batinfo@batcon.org Web site:

[Article by: Theodore H. Fleming, PhD]