|Townsend's Big-eared Bat, Corynorhinus townsendii|
The microbats constitute the suborder Microchiroptera within the order Chiroptera (bats). They are most often referred to by their scientific name. Other English names are "insectivorous bats", "echolocating bats", "small bats", or "true bats". All these names are somewhat inaccurate, because not all microbats feed on insects, and some of them are larger than small megabats.
The distinctions between microbats and megabats are:
- Microbats use echolocation, whereas megabats do not typically. (The Egyptian fruit bat Rousettus egyptiacus is an exception, but does not use the larynx echolocation method of microbats, instead giving scientists the theory that it clicks using its nasal passages and back of its tongue.)
- Microbats lack the claw at the second finger of the forelimb. This finger appears thinner and almost bonded by tissue with the third finger for extra support during flight.
- Megabats always lack a tail, whereas this trait only occurs in certain species of microbats.
- The ears of microbats possess a tragus (thought to be crucial in echolocation) and are respectively larger than megabat ears, whereas megabat ears are comparatively small and lack a tragus.
- Megabat eyes are quite large, whereas microbat eyes are comparatively smaller.
Most microbats feed on insects. Some of the larger species hunt birds, lizards, frogs, smaller bats or even fish. The three species of microbats that feed on the blood of large mammals or birds (vampire bats) exist in the Americas south of the United States. Microbats are 4 to 16 cm long. Leaf-nosed microbat species are not all known to be fruit and nectar-eating. Three species of leaf-nosed bats follow the bloom of columnar cacti in northwest Mexico and Southwest United States northward in the spring and then the blooming agaves southward in the fall. Yet other leaf-nosed bats, such as Vampyrum spectrum of South America, hunt a variety of prey such as lizards and birds. The horseshoe bats of Europe, though, have an incredibly intricate leaf-nose for echolocation and feed primarily on insects. Finally, the California leaf-nosed bat of North America is yet another insectivore to have this trait, as its name indicates.The term "leaf-nose," despite common fallacy, applies to a great variety of microbats and does in no way dictate the variety of diet a species with this trait prefers.
Microbats generate ultrasound via the larynx and emit the sound through the nose or the open mouth. Microbat calls (help·info) 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 20 to 20,000 Hz). The emitted vocalizations form a broad beam of sound used to probe the environment, as well as communicate with other bats.
Some moths have developed a protection against bats. They are able to hear bats' ultrasounds and flee as soon as they notice these sounds, or stop beating their wings for a period of time to deprive the bats of the characteristic echo signature of moving wings on which they may home in. To counteract this, the bats may cease producing the ultrasound bursts as they near prey, and thus avoid detection.
While bats have been traditionally divided into megabats and microbats, recent molecular evidence has shown the superfamily Rhinolophoidea to be more genetically related to megabats than to microbats, indicating the microbats are paraphyletic. To resolve the paraphyly of microbats, the Chiroptera were redivided into suborders Yangochiroptera (which includes Nycteridae, vespertilionoids, noctilionoids, and emballonuroids) and Yinpterochiroptera, which includes megabats, rhinopomatids, Rhinolophidae, and Megadermatidae.
This is the classification according to Simmons and Geisler (1998):
- Family Rhinopomatidae (mouse-tailed bats)
- Family Craseonycteridae (bumblebee bat or Kitti's hog-nosed bat)
- Family Rhinolophidae (horseshoe bats)
- Family Nycteridae (hollow-faced bats or slit-faced bats)
- Family Megadermatidae (false vampires)
- Family Natalidae (funnel-eared bats)
- Family Myzopodidae (sucker-footed bats)
- Family Thyropteridae (disk-winged bats)
- Family Furipteridae (smoky bats)
- 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)
- Whitaker, J.O. Jr, Dannelly, H.K. & Prentice, D.A. (2004) Chitinase in insectivorous bats. Journal of. Mammalogy, 85, 15–18.
- A Natural History of the Sonoran Desert, Edited by Steven Phillips and Patricia Comus, University of California Press, Berkeley p. 464
- Walker's Bats of the World, Ronald M. Nowak (1994)
- Teeling, E. C.; Madsen, O.; Van de Bussche, R. A.; de Jong, W. W.; Stanhope, M. J.; Springer, M. S. (2002). "Microbat paraphyly and the convergent evolution of a key innovation in Old World rhinolophoid microbats". Proceedings of the National Academy of Sciences of the United States of America 99 (3): 1431–1436. doi:10.1073/Pnas.022477199.