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Eumops glaucinus - Wagner’s Bonneted Bat

Physical Description:

Wagner’s Bonneted bat also known as the mastiff bat is a medium-sized bat, when compared to other members of its genus, with the largest of the species occurring in Bolivia and Paraguay (Best et al. 1997).  This species has a dark color to its coat, but variation in coat color is common.  Generally the backside ranges from a glossy black to light brown and the under parts are lighter, usually gray (Belwood 1992; Best et al. 1997).  Not only is the pelage of this species bicolored, but also are the individual hairs.  Each hair is short with a dark tip and a pale base (Best et al. 1997).

            What separates E. glaucinus from other species is the morphology of its appendages.  The nose is extended; a keel-like projection that protrudes from above the eyes (Best et al. 1997), and a tail is present (Belwood 1992; Bowles et al. 1990).  A defining trait in E. glaucinus is its large leathery ears that curve around to meet in the middle of the forehead and then advance forward (Bellwood 1992; Best et al. 1997).  In addition to the ears is a tragus, which aids in echolocation.  The tragus in this species is a well-developed structure that is wide and square across the top and protrudes from below the ears (Bellwood 1992; Best et al. 1997).  Both sexes of E. glaucinus are similar, however the males are larger than the females (Bowles et al. 1990), and the males posses a gular-thoracic gland (Best et al. 1997).


This species has a distribution that centralizes around the tropics.  According to Best et al. and Belwood (1997; 1992), in North America the range starts in central Mexico, extends south through Central America, and reaches as far south as Uruguay in South America.  In addition to this range, mastiff bats have been found on the islands of Cuba and Jamaica.  A subspecies, E. glaucinus floridanus, has had sporadic occurrences in southeastern Florida (Belwood 1992; Robson 1989).

Ontogeny and Reproduction:

E. glaucinus is a polyestrous (Best et al. 1997), however, only one litter which consists of only one young is produced each year (Best et al. 1997; Bowles et al. 1990).  Gestation generally takes place throughout spring (Bowles et al. 1990), but a fetus may be aborted due to stressful circumstances (Robson et al. 1989).  The birthing season occurs in late summer and continues into autumn (Best et al. 1997; Robson et al. 1989).  Therefore, the actual time of birth varies widely across the entire distribution of this species due to the changes in climate.  However, births are simultaneous among individuals in the same area and the majority of births occur at the end of June (Bowles et al. 1990).

Ecology and Behavior:

As stated before, mastiff bats are found in regions of the tropics (Best et al. 1997; Belwood 1992).  However, the type of tropical habitat that this species is found in varies, again due to the wide range of climates throughout its distribution.  These habitats include subtropical moist or dry forests, tropical moist forests, deserts, scrublands, and montane forests (Best et al. 1997). 

Daytime roost sites generally consist of tree cavities that are a result of woodpecker activity (Best et al. 1997).  However, they have been known to make use of buildings, particularly roofing tiles (Best et al. 1997).  This species is gregarious (Belwood et al. 1990; Best et al. 1997), however what is normally observed is a sex ratio of one male and his harem, which he will protect via high-pitched warnings (Best et al. 1997).

These bats feed primarily on flying insects, such as beetles, moths and mosquitoes, which are found near water (Best et al. 1997).  As long as these food sources are available it does not matter if the body of water they live near is natural or artificial (Bowles et al. 1990).

            According to Best et al. (1997) most activity starts right after sunset and continues throughout the night, ending shortly before sunrise.  However, cool temperatures will result in inactivity.  These swift fliers use agility and echolocation in order to locate prey, and therefore need open areas, and are often found feeding at high altitudes (Belwood et al. 1990; Best et al. 1997).

Literature Cited:

Belwood, J.J. Rare and endangered biota of Florida. Mammals.  1992.  University Press of Florida. Pgs. 216-223.


Best, T., M. Kiser, J. Rainey. 1997. Eumops glaucinus. Mammalian Species 551:1-6.


Bowles, J.B., P.D. Heideman, and K.R. Erickson. 1990. Observations on six species of free-tailed bats (Molossidae) from Yucatan, Mexico. The Southwest Naturalist 35:151-157.


Robson, M.S., F.J. Mizzotti, and T. Parrott. 1989. Recent evidence of the mastiff bat in southern Florida. Florida Field Naturalist 17:81-82.


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

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