Eumops bonariensis - Dwarf Bonneted Bat​

Phil Myers (photographer, copyright_holder),

Physical Description:

The Peter’s Mastiff Bat (E. Bonariensis) belongs to the genus Eumops and is the smallest of the eight species (Hunt et al. 2003).  Upper body parts were found to be reddish to blackish-brown often speckled with gray hairs.  Underside of body colored dingy to a similar gray as on upper portion of body (Sanborn 1932).  Colors may vary with geographical location in Paraguay, with northwestern Chaco E. bonariensis being paler than E. bonariensis from eastern Chaco and Paraguay (Hunt et al. 2003).  Ears are broad and connected by a thin skin and when projected forward they reach out past the tip of the proboscis.  Lips appear smooth and upper lip has many stiff, short hairs which project downward.  Proboscis is broad and upper incisors are hook-like (Sanborn 1932).

 This genus is thought to be a related link or transitional genus between other species of the family Molossidae.  Comparable characteristics include the third commissure and metacone, in Eumops these characters are either absent or very minute, whereas in other genera (Tadarida, Chaerephan, and Platymops) these attributes are apparent on the third upper molar.  The tragus can also be considered an intermediary trait which is either very small or broad and flat (Sanborn 1932).

Distribution:

In South America E. bonariensis arise around the Patagonian subreigion, eastern Brazilian highlands and coast, the Amazon Basin, the northern coast islands, and the Pacific coast f Colombia and Ecuador.  Eumops bonariensis occurs in Panama to Patagonia in South America with the exemption of all the west coast.  In Panama they are thought to have a very limited distribution which is constrained to the xeric coastal lowlands along the drainage of the Rio Piedras and Rio Chirigugua in southeastern Chiriqui (Dolan and Carter 1979).  E. bonariensis appear around altitudes of 240 m in Panama, sea level to 1,000 m in Colombia, and 80 m in Venezuela (Hunt et al. 2003). 

Distribution of Eumops bonariensis in North and South America, 1, E. b. beckeri;  2,  E. b. bonariensis;  3, E. b. delticus; and 4, E. b. nanus.  Map source (Hunt et al. 2003).

Ontogeny and Reproduction:

Research in Yucantan, Mexico has indicated that adult males had testes 3 – 5 mm in average length during March and May, 4 mm in September and October (Birney 1974).  In Argentina one male had abdominal testes and another had scrotal testes in mid-July.  On average the male’s glans penis was 1.5 – 2.5 mm in length.  The external covering of the glans penis is free of epithelial spines.  It is oval at the origin and expands distally to form 3 prominent lobes.  One is dorsal and the other two are lateral which connect along ventral midline and produce a V-shaped furrow that terminates at the urinary meatus (Birney 1974).

Two females were captured during November in Bolivia and when examined were discovered to have single embryos.  Also in Yucantan, Mexico two other females were captured which had fetuses, one measuring 8 mm in crown-rump length and the other measuring 16 mm in crown-rump length during the month of March (Mares et al. 1995). 

Ecology and Behavior:

In Paraguay, E. bonariensis was found in many diverse areas.  In all it was captured in six of the country’s seven biomes (Willig et al. 2000).  In the Paraguayan Chaco, the Dwarf bonneted bat was commonly found around homes.  They will often roost in the roofs of the homes that are made of overlapping, split, palm logs.  Research has indicated that they will use the same roosting sites for a number of years and even then they may not drift too far away.  Research has also indicated that they will roost with other species.

They also were found being active over small ponds during evening and early morning hours.  E. bonariensis is an insectivore.  Its diet has been known to contain Lepidoptera, Coleoptera, Hemiptera, Scarabaeidae, and other unidentified insects (Hunt et al. 2003).  They fly high and fast and have been captured in mist nets.  While resting and throughout activity E. bonariensis emanate high-pitched calls that are audible to humans.  

Literature Cited:

Bat Conservation International Website. www.batson.org (Accessed 2 December 2004).

Briney, E. C., J. B. Bowles, R. W. Timm, and S. L. Williams.  1974.  Mammalian distributional records in Yucatan and Quintana Roo, with comments on reproduction, structure, and status of peninsular populations. Bell Museum of Natural History, University of Minnesota, Occasional Papers 13:1-25.

Brown , R. E.  1967.  Bacula of some New World molossid bats.  Mammalia 31:645-  667.

Dolan, P. G., and D. C. Carter.  1979.  Distributional notes and records for Middle American Chiroptera.  Journal of Mammalogy 60:644-649. 

Edger, J. L.  1977.  Systematics of the Genus Eumpos (Chiroptera: Molossidae). Life Sciences Contributions, Royal Ontario Museum 110:1-69.

Freeman, P. W.  1981.  A multivariate study of the Family Molossidae (Mammalia, Chiroptera): morphology, ecology, evolution.  Fieldiana: Zoology, new series 7:1-309.

Hunt, J. L., L. A. McWIllians, T. L. Best, and K. G. Smith.  2003. Eumops Bonariensis.  Mammalian Species 733:1-5. 

Ibanez, C., and J. Ochoa G.  1989.  New records of bats from Bolivia.  Journal of Mammalogy 70:216-219.

Koopman, K. E.  1994.  Chiroptera: systematics.  Handbook of zoology: a natural history of the phyla of the animal kingdom. VIII. Mammalia. Walter de Gryyter, New York. 

Labbe, J. 2001. "Eumops bonariensis" (On-line), Animal Diversity Web. Accessed December 02, 2004 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Eumops_bonariensis.html.

Mares, M. A.,  R. A. Barquez, and J. K. Braun.  1995.  Distribution and ecology of some Argentine bats (Mammalia). Annals of Carnegie Museum 64:219-237.

Sanborn, C. C.  1932.  The bats of the genus Eumops.  Journal of Mammalogy 13:347-357.

Willig, M. R., S. J.  Presley, R. D. Owen, and C. Lopez-Gonzalez.  2000.  Composition and structure of bat assemblages in Paraguay: a subtropical-temperate interface.  Journal of Mammalogy 81:386-401.

Reference written by Jeremy Mueller, Biol 378 (Mammalogy), University of Wisconsin – Stevens Point:  Edited by Christopher Luddington. Page last updated 02-17-05.