Microbat

Microbats
Townsend's Big-eared Bat, Corynorhinus townsendii
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Chiroptera Suborder: Microchiroptera Dobson, 1875
Superfamilies
Emballonuroidea Rhinopomatoidea Rhinolophoidea Vespertilionoidea Molossoidea Nataloidea Noctilionoidea

Microbat is the common name for any of the bats comprising the suborder Microchiroptera of the order Chiroptera (bats), characterized by true wings and flight (as with all bats), lack of claws on the second digits, lack of underfur, and ears that generally have large pinnae and do not form a closed ring, but rather have edges that are separated from each other at the base of the ear. Unlike most members of the second order of bats, the megabats comprising the suborder Megachiroptera, the microbats use sophisticated echolocation for orientation. Mircrobats also are known as "insectivorous bats," "echolocating bats," and "small bats." All these names are somewhat inaccurate, because not all microbats feed on insects, there is one genus of megabats that use a simple (but unrelated) form of echolocation, and some microbat species are larger than small megabats.

Overview and description

Bats comprise the mammalian order Chiroptera and traditionally are divided into the two distinct groups, typically suborders, of Microchiroptera, or microbats, and Megachiroptera, or megabats. Although these names imply that microbats are smaller than megabats, this is only true in a general since, as some microbat species are larger than some megabat species. However, there remain consistent differences in other physical and ecological aspects.

Among distinctions between the two suborders is that microbats lack the underfur characteristic of megabats and have only guard hairs or are naked; microbats lack the claw at the second toe of the forelimb which is characteristic of all but one of the megabats; and the ears of microbats tend to have large, complex pinnae (external ear)s that include an enlarge tragus or antitragus (Wund and Myers 2005). In addition, microbats tend to have small eyes, while megachiropterans tend to have large prominent eyes. Furthermore, the dentition or cheek teeth of microbats generally can easily be related to dilambdodont teeth, whereas megabats have simplified cheek teeth that are difficult to interpret (Wund and Myers 2005). And, as a major distinction, microbats use echolocation, whereas megabats do not typically, with the exception of members of the genus Rousettus, which have a simplifed, unrelated form of echolocation.

There also are important ecological differences, as megabats typically are herbivorous, consuming fruit, nectar, and pollen, while microbats often are insectivorous, but also have a variety of other feeding behaviors. While most microbats feed on insects, some of the larger species hunt birds, lizards, frogs ,or even fish. Microbats that feed on the blood of large mammals (vampire bats) exist in the Americas south of the United States. Many species have chitinase enzymes in their intestines that are produced by symbiotic bacteria. These help in digesting the insect prey (Whitaker et al. 2004).

Microbats typically are 4 to 16 centimeters (1.5 to 6 inches) long. The smallest bat is the microchiropteran Craseonycteris thonglongyai, which is about the size of a large bumblebee and may be the world's smallest mammal. It weight only 2 to 3 grams and has a head and body length of 29 to 33 millimeters (1.1 to 1.3 inches), and a forearm length that ranges from 22 to 26 millimeters (0.9 to 1.0 inches)(Goswami 1999; Wund and Myers 2005).

Microbats have a wider distribution than the Old World megabats and are found in both the Old World and New World.

Echolocation

Bats are one of the most famous examples for echolocation among animals. All microbats use echolocation. The only megabat which is known to echolocate is the genus Rousettus, which uses a different method of echolocation than that used by microbats. The echolocation system of bats is often called biosonar.

Microbats generate ultrasound via the larynx and emit the sound through the nose or the open mouth. Microbat calls range in frequency from 14,000 to over 100,000 hertz, well beyond the range of the human ear. (Typical human hearing range is considered to be from 20Hz to 20,000 Hz.) The emitted vocalizations form a broad beam of sound that is used to probe the environment.

Some moths have developed a protection against bats. They are able to hear the bat's ultrasounds and flee as soon as they notice these sounds, or stop beating their wings for a period of time to deprive the bat of the characteristic echo signature of moving wings, which it may home in on. To counteract this, the bat may cease producing the ultrasound bursts as it nears its prey, and can thus avoid detection.

Classification

There are about 17 families with almost 800 species of microbats, typically organized into seven superfamilies. Following is the classification according to Simmons and Geisler (1998):

Superfamily Emballonuroidea

• Family Emballonuridae (sac-winged bats or sheath-tailed bats)

Superfamily Rhinopomatoidea

• Family Rhinopomatidae (mouse-tailed bats)
• Family Craseonycteridae (Bumblebee bat or Kitti's hog-nosed Bat)

Superfamily Rhinolophoidea

• Family Rhinolophidae (horseshoe bats)
• Family Nycteridae (hollow-faced bats or slit-faced bats)
• Family Megadermatidae (false vampires)

Superfamily Vespertilionoidea

• Family Vespertilionidae (vesper bats or evening bats)

Superfamily Molossoidea

• Family Molossidae (free-tailed bats)
• Family Antrozoidae (pallid bats)

Superfamily Nataloidea

• Family Natalidae (funnel-eared bats)
• Family Myzopodidae (sucker-footed bats)
• Family Thyropteridae (disk-winged bats)
• Family Furipteridae (smoky bats)

Superfamily Noctilionoidea

• Family Noctilionidae (bulldog bats or fisherman bats)
• Family Mystacinidae (New Zealand short-tailed bats)
• Family Mormoopidae (ghost-faced bats or moustached bats)
• Family Phyllostomidae (leaf-nosed bats)

References

ISBN links support NWE through referral fees

Goswami, A. 1999. "Craseonycteris thonglongyai" (On-line), Animal Diversity Web. Accessed October 19, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Craseonycteris_thonglongyai.html.

• Pettigrew, J. D., B. G. Jamieson, S. K. Robson, L. S. Hall, K. I. McAnally, and H. M. Cooper. 1989. Phylogenetic relations between microbats, megabats and primates (Mammalia: Chiroptera and Primates). Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 325(1229):489-559.

Simmons, N. B., and J. H. Geisler. 1998. Phylogenetic relationships of Icaronycteris, Archeonycteris, Hassianycteris, and Palaeochiropteryx to extant bat lineages, with comments on the evolution of echolocation and foraging strategies in microchiroptera. Bulletin of the American Museum of Natural History 235: 1-182.

• Wund, M., and P. Myers. 2005. Chiroptera. Animal Diversity Web. Retrieved October 19, 2008.

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