Emballonuridaesac-winged bats, sheath-tailed bats, and relatives
Emballonurids are known as sac-winged or sheath-tailed bats. The first of these names describes the glandular sac usually found on the propatagium (leading edge of the wing) in many species. This gland produces a scent used in social displays and to mark territories. Males of some species have a pouch at the base of the throat that may serve a similar function. Emballonurids are also known as sheath-tailed bats because their tail appears to be sheathed in a membrane (uropatagium or interfemoral membrane). The tip of the tail protrudes from the top of this membrane and does not extend for the full length of the membrane.
This family includes 13 genera and 47 species. Their range is tropical and subtropical in both the Old and the New World.
Most emballonurid are brown or grey in color, but this family also includes the whitish ghost bats ( Diclidurus) and bats with a pair of white stripes down the back ( Saccopteryx). Bats of this family are small to medium sized (5 to 105 g) and have a smooth face and lips, lacking the noseleafs or nose ornaments found in some other bat families. Emballonurid ears are usually simple, round, and cup-shaped. They are often united by a band of skin across the forehead, and a tragus is present (a fleshy lobe that protrudes from the ear).
The muzzle of emballonurids is usually short and broad, and there are inflated sinuses in the maxillae. of the rostrum. Other skull characters used to distinguish this family are the following: the presence of a postorbital process (often well developed); small premaxillae that lack palatal branches and that are not fused to each other or to the adjacent maxillae; and a palate that ends beyond the plane of the last molars.
Emballonurids have 30 to 34 teeth: 1-2 upper incisors, 2-3 lower incisors, 1 upper and 1 lower canine, 2 upper and 2 lower premolars, and 3 upper and lower molars. The cheek teeth have a W pattern of cusps and ridges ( dilambdadont), which is good for breaking up the insects they eat. These bats are primarily insectivorous (although they have been observed to eat fruit on occasion) and hawk insects in flight. Their long narrow wings allow them fast flight but make them somewhat less maneuverable than bats of some other families that characteristically have broader wings. The 2nd finger has no phalanges, and the third has only 2.
Like all microchiropterans, emballonurids use echolocation to locate prey. Interestingly, there is also some evidence that bats in this family may use echolocation for communication.
Emballonurid bats shelter in rocky crevices, caves, ruins, houses, trees, leaves, and hollow logs; their roosts tend to be more exposed than those found in some other bat families. Some emballonurids live in stable year-round harems of 1-8 females in a territory patrolled by the male. This mating system is known as resource defense polygyny. Other members of this family are solitary or colonial. Colonies of Coelura afra include up to 50,000 bats, each of which returns to a precise place in a roosting cave along the Kenyan coast.
The fossil record of emballonurids extends to the late Eocene or early Oligocene.
References and literature cited:
Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. 1999. Mammalogy. Adaptation, Diversity, and Ecology. WCB McGraw-Hill, Boston. xii+563pp.
Anderson, S. and J. K. Jones, Jr., 1984. Orders and Families of Recent Mammals of the World. John Wiley and Sons, New York. 686pp.
Fenton, M. B., P. Racey, and J.M. V. Rayner (eds.), 1987. Recent Advances in the Study of Bats . Cambridge University Press, Cambridge.
Hill, J. E. and J. D. Smith, 1992. Bats: A Natural History . University of Texas Press, Austin.
Nowak, Ronald M., 1994. Walker's Bats of the World . Johns Hopkins University Press, Baltimore.
Ransome, Roger, 1990. The Natural History of Hibernating Bats . Christopher Helm, London.
Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. Fourth Edition. Saunders College Publishing, Philadelphia. vii+565pp.
Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.
Contributors
Laurel Hester (author), Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.
Glossary
- bilateral symmetry
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having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- chemical
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uses smells or other chemicals to communicate
- endothermic
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animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- motile
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having the capacity to move from one place to another.
- sexual
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reproduction that includes combining the genetic contribution of two individuals, a male and a female
- tactile
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uses touch to communicate