Eptesicus brasiliensis - Brazilian brown bat​

Physical Description:

Eptesicus brasiliensis (Demarest 1819), the Brazilian brown bat has been considered a large bat by some (Barquez 1993) and a medium by others (Eisenberg 1999). Basic measurements include: total length, 101-107; tail, 37-49; foot, 8-11; ear, 16-18; forearm, 41-45; and dental formula 2/3, 1/1,1/2, 3/3 = 32 (Braquez 1993). This bat varies in its coloration throughout its range, from gray with a yellow cast dorsally with a grey/white venter to dark brown with a red cast and a yellowish venter (Eisenberg 1999). Other characteristics of the Brazilian brown bat include the appearance of a swollen snout, a hairless uropatagium and a rounded tragus (Barquez 1993). The technical description includes dental characters: the upper incisors are of unequal size and a single premolar on each side (Barquez 1993).

Davis (1966) and Koopman (1978) recognize several subspecies of Eptesicus brasiliensis, including Eptesicus brasiliensis thomasi and Eptesicus brasiliensis andinus (Koopman 1978), and Eptesicus brasiliensis argentinus, and Eptesicus brasiliensis melanopterus, which may account for its physical variations throughout its range. These subspecies utilize different habitats within the larger range, and each possessing a certain coloration or size. When compared with the Brazilian brown bat, thomasi is smaller and paler, andinus has slightly longer body hair to complement its use of cool upland habitat, argentinus is the palest form of E. brasiliensis, and melanopterus is the smallest.

Distribution:

The Brazilian brown bat is found from Mexico in the northern portion of its range south to Paraguay, Uruguay and northern Argentina. This bat is widespread in its range, but is considered locally rare (Arita 1993).

Within Paraguay, research has shown the presence of the bat along the western edge of the country and in Chaco region (Fig. 1), which has been characterized by being flat, with forests or palms, low to medium precipitation with seasonal inundation in some locations, and semiarid to semihumid conditions (Willig et al. 2000). The earlier work by Koopman (1978) in Peru showed that the Brazilian brown bat used both Amazonian Highlands and Lowlands, possibly due to resource partitioning among several subspecies.

Fig. 1. According to Willig et. al (2000), Eptesicus brasiliensis, the Brazilian brown bat was found in both the Alto Chaco (AC) and the Bajo Chaco (BC) regions.

Ontogeny and Reproduction:

The paucity of information on the ontogeny and reproduction of the Brazilian brown bat necessitates generalization from what is known of other species in the genus Eptesicus. The related species Eptesicus furinalis, the Argentine brown bat and others produce between one and two young per litter, with northern temperate species having only one litter per year (Kurta 1990), and southern tropical species having up to two litters per year with variations in the gestation length depending on the season (Mies 1996). Overlap may also occur between lactation and gestation (Mies 1996). The young are born small and without hair, depending greatly on their mother’s care (Kurta 1990). Young Eptesicus may become sexually mature around one year of age (Mies 1996), but many do not reproduce during that first season (Kurta 1990).

Ecology and Behavior:

The Brazilian brown bat is an insectivorous bat that has been known to feed over tropical streams in some parts of its range, and can also be found feeding along edges of other habitats (Eisenberg 1999). There is evidence that the Brazilian brown bat does not roost in caves (Bredt 1999).

Remarks:

This rare bat can often be confused with other closely related bat species in the same region, including Eptesicus diminutus (Diminutive Serotine) and Eptesicus furinalis (Argentine Brown Bat), and is unreliably differentiated from them based on size, with the Brazilian brown bat being the largest (Barquez 1993).

The ecology and behavior of this bat species is very poorly understood and deserves increased research especially in regards to its feeding preferences and reproductive strategy.

Literature Cited:

Arita, Hector T. 1993. Rarity in Neotropical Bats: Correlations with Phylogeny, Diet, and Body Mass. Ecological Applications, 3(3): 506-517.

Barquez, Ruben M., Norbeto P. Giannini, Micheal A. Mares. Guide to the Bats of Argentina. (Guia de los Murcielagos de Argentina). 1993. Oklahoma Museum of Natural History: University of Oklahoma. 56, 102-103.  

Bredt, Angelika, Wilson Uieda, Edvard Dias Magalhaes. 1999. Cave Bats from the Distrito Federal area in Mid Western Brazil (Mammalia-Chiroptera). Revista Brasileria de Zoologia. 16(3):731-770.

Davis, W. B. 1966. Review of South American bats of the genus Eptesicus. Southwestern Naturalist, 11(2):245-274.

Eisenberg, John F., Kent Redford. Mammals of the Neotropical: The Central Neotropics. 1999. Volume 3.University of Chicago Press: Chicago. 99-100.

Koopman, K. F. 1978. Zoogeography of Peruvian bats with special emphasis on the role of the Andes. American Museum Novitates, 2651:1-33.

Kurta, Allen and Rollin H. Baker. 1990. Mammalian Species No. 356: Eptescius fuscus. The American Society of Mammalogists.

Mies, Rob, Allen Kurta, David G. King. 1996. Mammalian Species No. 526: Eptescius furnalis. The American Society of Mammalogists.

Willig, Michael R., Presley, Steven J., Owen, Robert D., López-González, Celia. 2000. Composition and Structure of Bat Assemblages in Paraguay: a SubTropical-Temperate Interface. Journal of Mammalogy, 81(2):386–401.

Reference written by Jessica Orlofske, Biology 378 student.  Edited by Christopher Yahnke. Page last updated 08-03-05.