vespertilionid

n.
Any of various widely distributed insect-eating bats of the family Vespertilionidae, characterized by a long tail.

adj.
Of or belonging to the family Vespertilionidae.

[From New Latin Vespertiliōnidae, family name, from Vespertiliō, Vespertiliōn-, type genus, from Latin vespertiliō, bat, from vesper, evening.]

(Vespertilioninae)

Class: Mammalia

Order: Chiroptera

Suborder: Microchiroptera

Family: Vespertilionidae

Thumbnail description
Small- to medium-sized bats with well-developed tails that in most species are completely covered by tail membranes

Size
Range about 1.4–5.5 in (3.5–14 cm) in body length, and about 0.09–1.59 oz (2.5–45 g) in weight

Number of genera, species
30 genera; about 267 species

Habitat
Forests and open fields, both moist and dry regions, lowlands and mountains up to the tree line

Conservation status
Extinct: 2 species; Critically Endangered: 6 species; Endangered: 17 species; Vulnerable: 46 species; Lower Risk: 59 species

Distribution
Old and New World from the tropics into temperate zones

Evolution and systematics

The subfamily of vespertilionines is by far the largest of the five subfamilies within the family Vespertilionidae. With 30 genera and about 267 species, it makes up more than 90% of all the species within Vespertilionidae, which itself is the largest bat family.

In the subfamily Vespertilioninae, the major genera include:

• Myotis, 84 species
• Pipistrellus, 50 species
• Eptesicus, 32 species
• Chalinolobus, 15 species
• Scotophilus, 10 species

Eighteen of the remaining genera each have fewer than five species, and half have only one representative species. The two-species genus Antrozous, or the pallid bats, is notable in that some systematists place it in its own family, Antrozoidae, or in its own subfamily, Antrozoinae, within the vespertilionids.

Phylogenetic studies indicate that the family Vespertilionidae is likely most closely related to the families Mystacinidae, or the New Zealand short-tailed bats, and Molossidae, or the free-tailed and mastiff bats.

Physical characteristics

Vespertilionines are wide-ranging. The bamboo bat (Tylonycteris pachypus) and African banana bat (Pipistrellus nanus) are not only the smallest in the subfamily at about 0.1 oz (3g) in weight, but also two of the tiniest bats in the world. At the opposite end of the spectrum is the subfamily's largest member: the large mouse-eared bat (Myotis myotis) with its nearly 14-in (35-cm) wingspan.

Although a large number of vespertilionines are brown, a few are frosted with silver, yellow, or reddish tips. The hoary bat (Lasiurus cinereus), for example, has a luxuriant pelage highlighted in white. Fur in other species within this subfamily may be golden like that of the yellow bat (Rhogeessa anaeus) of Belize, ginger and white like that of Welwitch's hairy bat (M. welwitschii) of Africa, or vivid orange like that of Myotis formosus of Southeast Asia.

Vespertilionines have some features in common. All lack the fleshy nose ornaments common to so many other bat families. In fact, the family Vespertilionidae is often called "the plain-faced bats." Most of the vespertilionines also have small eyes, although a few, such as the pallid bat (Antrozous pallidus), have noticeably larger eyes. Ear size can be small or large, with many species having tiny, rounded ears smaller than their head while others have enormous ears that extend almost the length of their bodies. The long-eared bat (Plecotus auritus) has extraordinarily long ears, but it can tuck them so far under the wing (done during the daily sleep and in hibernation) that only the pointed ear cover (tragus) can be seen.

Other distinctive features of vespertilionines—indeed all species within the family Vespertilionidae—are a well developed tragus that reaches up from the base of the ear, and a nearly naked patagium, or flight membrane, that covers the relatively long tail. Vespertilionine tails are commonly half as long as the body.

Distribution

Vespertilionines spread almost around the globe. The pipistrelles (Pipistrellus) include more than three dozen species in North America, Europe, Africa, Madagascar, Asia, and Australia. The noctule bats (Nyctalus) are distributed from the Azores through Europe and Asia to the Philippines, and the big brown bats (genus Eptesicus) are distributed nearly worldwide. The northern bat (E. nilssoni) has an extraordinary resistance to cold; its distribution extends into the Arctic. The mouse-eared bats (Myotis spp.) are especially noted for their wide distribution, and members of this genus are found almost everywhere bats exist.

Habitat

Given their nearly global distribution, it is not surprising that the habitat preferences of the vespertilionines vary greatly. While a large number of the temperate members inhabit caves during winter, their summer haunts can range from caves to woodlands, and riparian areas to deserts. A few vespertilionines stay away from disturbed areas, but many, like the serotine bat (Eptesicus serotinus), will make use of cracks and crevices in human-made structures for roosts. Many species utilize tree hollows and loose bark for daytime roosts in the summer, with various southern species even taking advantage of these spots for hibernation. A few more tropical species make use of vegetation for their roosts. The African banana bat (Pipistrellus nanus), for example, invariably spends the day in young banana leaves that are still rolled up.

Behavior

Temperate vespertilionines hibernate—sometimes alone, sometimes in the hundreds. Commonly, individuals awaken periodically during the winter. If the outside temperature is warm enough, they will travel outside of the hibernaculum, which may be a cave, attic, or tunnel, and look for food. Following hibernation, male bats in this subfamily will typically spend the summer alone, while females will group together in maternity colonies to bear and raise their young. A maternity colony of pipistrelles (Pipistrellus pipistrellus), for example, may include more than 100 females. Unlike most vespertilionines, pipistrelle nursing colonies may include some males. After the young are independent, the bats abandon these sites.

Mouse-eared bats generally return to the same summer and winter roosts, which may be as much as 125 mi (200 km) away from each other. Another change of roosts is occasionally made in summer or in winter. Roost changes are also typical of other vespertilionine species.

Most species begin mating in the fall, but very little is known about courtship behaviors. The little brown bat (Myotis lucifugus), which is one of the most well-known bats in the New World, engages in no courtship. Mating simply involves the male grasping the female by the nape of her neck during copulation, performed upside down. The two separate after copulation, often to find additional partners.

In the fall, many temperate vespertilionines disappear from northern habitats, assumedly to migrate south, although some species' seasonal movements are little known. The hoary bat is one species whose migration pattern is generally understood, although specifics are still lacking. These bats begin migrating in late summer to early fall, with often-large, mixed-sex groups traveling to the Gulf states and Mexico to spend the winter. However, the destination of some individual populations is still in question. For instance, populations of the red bat (Lasiurus borealis) of North America that spend their summers in the upper Great Lakes may not fly as far south as more southern populations, perhaps migrating only as far as the Ohio River valley for the colder months instead of the Gulf states or Mexico. Part of the mystery surrounding many bat migratory movements stems from their hibernacula, which are often hidden, remote, and undiscovered. Return migrations for many species, including the hoary bat, begin when gravid females head north. The males follow shortly thereafter.

Vocalizations are used for communication and carry a variety of information. Acoustic studies on hoary bats show that they use mainly multiharmonic signals with considerable intra- and inter-individual variability in five signal variables (call duration, call interval, highest, lowest frequency, and frequency with maximum energy) to recognize each other and communicate with one another. Echolocation behavior is influenced by the presence of conspecifics. When bats hunt together, call duration decreases and call interval increases. While hunting, the pallid bat flies slowly, and close to the ground, with rhythmic dips and rises. Instead of echolocating, the desert-adapted pallid bat relies on sounds made by its prey to locate and capture a meal, often crickets or scorpions.

Some species (pallid bats) are known to produce a musky skunk-like odor from glands on the muzzle. There have been no experimental studies to determine the function of this odor—it may be a defense mechanism for repelling predators.

Feeding ecology and diet

The bats in this group are almost exclusively insectivorous. Armed with echolocation capability, these skilled flyers are typically able to catch moths, beetles, flying ants, and other insects on the wing, but many will also glean leafhoppers, spiders, or other arthropods off of foliage. A few have expanded their diet to include fish or other vertebrates. Remains of food under feeding sites of the pallid bat (Antrozous pallidus) have included bugs, crickets, and locusts, and occasionally scorpions, lizards, and geckos. The Mexican fishing bat (Pizonyx visesi) employs its long hindfoot claws to spear fish. Daubenton's bat (Myotis daubentonii) also occasionally eats fish.

Vespertilionines commonly rest during the day in roosts, and forage at night. Some species, like the western barbastelle (Barbastella barbastellus) become active early in the evening and hunt for a few hours. Noctules leave their sleeping site early, and may begin the hunting flight in the afternoon, particularly in the fall. The spotted bat (Euderma maculatum) is active through the night. All typically rest between foraging flights to aid digestion.

Predation on these bats is generally rare. Predators may include owls who catch and kill a bat while it is foraging for insects, or mammals, like raccoons or skunks, and snakes that may find a daytime roost.

Reproductive biology

This subfamily of bats generally begins mating in the fall. Females store sperm in the reproductive tract after mating and during hibernation and then ovulate in the spring. In some species, such as the big brown bat (Eptesicus fuscus), mating also occurs in the spring. Gestation averages about two months, with altricial young typically born in late spring or early summer. Litter size is commonly one or two pups, although some species produce more. During birth, most females turn right side up and catch the infant in the tail membrane. Hoary bats and red bats have four teats, and occasionally raise four pups. On average, females lactate for one to two months. During the same period, the young learn to fly from their mothers just three weeks after birth on average and begin to forage on their own. The young may become independent during the first year, or spend the winter with the family unit. They are often left in roosts with hundreds of other bats. Females of many species become sexually mature the first year, while males typically mature the following year. Compared to mammals of a similar size, bats can live a very long time. They average 10 years or so but records of bats living 15 years and longer under natural conditions are not uncommon and there is one record of a little brown bat surviving for at least 32 years in the wild.

Conservation status

Many vespertilionines are experiencing population declines, particularly due to habitat destruction. A large number of these bats roost in dying or dead trees, as well as abandoned buildings, which are often targeted for removal.

Legislative, organizational and grassroots efforts are now under way to protect populations. The Indiana bat (Myotis sodalis), for example, is listed as Endangered by the IUCN. The U. S. Fish and Wildlife Service lists the causes of the decline as habitat disturbance, destruction and degradation, and pesticide use. Also listed as endangered under the U. S. Endangered Species Act, the species is protected from hunting or harassment. In addition, ongoing programs are managing bat habitats to ensure that species have sufficient roosting and hibernation sites, and to help educate the public on the bat's plight.

Concerned individuals have also become involved in the decline of vespertilionines and other species, and made various artificial roosts, like bat houses, more popular. According to Paul A. Racey of the U. K.'s Bat Conservation Trust, "Instead of trying to get rid of bats in their attics or other spaces, many home owners frequently ask bat workers how they can attract bats to their house. To accommodate bats, special roofing tiles and clay bricks that facilitate the entry of bats to roof spaces are now marketed in the U. K."

Significance to humans

Bats have major cultural importance, especially in Asia. But perhaps the greatest significance of bats to humans stems from their insectivorous diet. A single vespertilionine can eat thousands of insects a night, and many of these arthropods are seen as pest species. For instance, bats help control populations of mosquitoes, flies, moths, beetles, and other insects. While decreases in fly or mosquito populations are readily seen as a benefit for all humans, unchecked populations of beetles, moths, and other pest species can cause significant damage to agricultural crops and forests.

In addition, many vespertilionine bats are very susceptible to pesticides and other chemicals, making them good bioindicators. These bats carry rabies and other zoonotic diseases of concern to humans.

Species accounts

Pallid bat
Western barbastelle
Big brown bat
Spotted bat
Allen's big-eared bat
Silver-haired bat
Hoary bat
Little brown bat
Noctule
Evening bat
Eastern pipistrelle
Brown long-eared bat
Bamboo bat
Daubenton's bat

Resources

Books:

Altringham, J. Bats: Biology and Behavior. Oxford: Oxford University Press, 1996.

Fenton, M. Bats. New York: Checkmark Books, 2001.

Kunz, T., and P. Racey, eds. Bat Biology and Conservation. Washington, DC: Smithsonian Institution Press, 1998.

Kurta, A. Mammals of the Great Lakes Region. Ann Arbor: The University of Michigan Press, 1995.

Nowak, R. Walker's Mammals of the World. Baltimore: Johns Hopkins University Press, 1999.

Periodicals:

Adams, R., and S. Pedersen, "Wings on Their Fingers." Natural History 103 (January 1994): 48–55

Arizona Game and Fish Department. "Antrozous pallidus." Unpublished abstract compiled and edited by the Heritage Data Management System, Arizona Game and Fish Department. Phoenix: 1994.

Bradley, P. "Nevada's Night Fliers." Natural History 105 (February 1996): 72–6.

Milius, S. "Bat Bites Bird—In Migration Attacks." Science News 160, no. 6 (2001): 86.

Petit, E., L. Excoffier, and F. Mayer. "No Evidence of Bottleneck in the Postglacial Recolonization of Europe by the Noctule Bat (Nyctalus noctula)." Evolution 53, no. 4 (1999): 1247–1258.

Racey, P. "The Conservation of Bats in Europe." Bats 10, no. 4 (1992): 4–10.

Whitaker, John O., Jr. "Food of the Big Brown Bat Eptesicus fuscus from Maternity Colonies in Indiana and Illinois." The American Midland Naturalist 134 (1995): 346–360.

Organizations:

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:

The Bat Conservation Trust. 15 Cloisters House, 8 Battersea Park Rd., London, SW8 4BG UK. Phone: 020 7627 2629. Fax: 020 7627 2628. E-mail: enquiries@bats.org.uk Web site:

The Organization for Bat Conservation at Cranbrook Institute of Science. 39221 Woodward Avenue, P.O. Box 801, Bloomfield Hills, MI 48303-0801 USA. Phone: (800) 276-7074. E-mail: obcbats@aol.com Web site:

[Article by: Leslie Ann Mertz, PhD]

Note: click on a word meaning below to see its connections and related words.

The noun has one meaning:

Meaning #1: a variety of carnivorous bat
  Synonym: vespertilian bat

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