Phyllostomus discolor - Pale spear-nosed bat​

Physical Description:

Phyllostomus discolor is known to be one of the smallest species of the genus (Redford and Eisenberg 1999).  Its coloration is dark brown to tan with white tips and short, soft pelage.  P. discolor is stout-bodied and has a short tail that pierces the tail membrane.  The tail length ranges from 10-25mm (Norwalk 1999).

P. discolor has an average forearm length of about 61mm.  In males, the head and body length averages 83.6mm and the average weight is 38.2g.  Females have an average head and body length of 84.2mm and an average weight of 35.4g. (Redford and Eisenberg 1999)

The dental formula of Phyllostomus discolor is as follows: 2/2, 1/1, 2/2, 3/3=32 (Redford and Eisenberg 1992).  It has a long and narrow muzzle, a noseleaf, and widely separated ears.  Many species of this genera are polymorphic (absent or one vibrissa), in P. discolor the interramal vibrissae are absent (Wetterer et al 2000).  The lower lip has a V-shaped groove edged with wartlike protuberances (Nowak 1999).

Distribution:

The pale spear-nosed bat occurs from southern Mexico south to southeastern Brazil, Peru, and northern Argentina (Redford and Eisenberg 1999).  It has also been recorded in eastern Paraguay (Redford and Eisenberg 1992). 

Koopman (1982) recognizes a series of faunal provinces for phyllostomid bats in South America.  The provinces recognized by Koopman for P. discolor are: Eastern Brazilian highland and coast, Amazon Basin, Northern coast and islands, Pacific coast of Columbia, Ecuador, and extreme northwestern Peru, and Middle America (Figure 1).

Distribution of Phyllostomus discolor in South America (Koopman 1982).

Ontogeny and Reproduction:

Phyllostomus discolor may have a sex ratio of one male to twelve females in breeding roosts, suggesting harem formation (Redford and Eisenberg 1999).  This species may be acyclic or a continuous breeder in some areas.  In Costa Rica, it could be monoestrous (one reproductive bout per year) (Nowak 1999). 

Ecology and Behavior:

P. discolor is found in mature and secondary rainforest, gardens and plantations, gallery forest, dry forest, and cloud forest (Emmons 1990).  Most specimens taken in Venezuela were below an elevation of 500m (Redford and Eisenberg 1999). 

Phyllostomus discolor roosts in groups of 25 in hollow tree trunks (Redford and Eisenberg 1999).  Emmons (1990) found that several P. discolor fly single file to forage.  Neuweiler (2000) also found that P. discolor, depending on food availability, will go in groups of 2-15 individuals to visit flowers and fruit bearing trees.  Phyllostomus discolor is known to mainly eat fruit, pollen, nectar, and insects (Nowak 1999).

Remarks:

Most species in the Subfamily Phyllostominae retain the tail and a well-developed uropatagium, but others show tail reduction and varying degrees of reduction of the uropatagium.  Small phyllostomids are unable to maintain a constant body temperature in extreme cold.  The New World phyllostomid bats are convergent with patterns shown by the Pteropodidae with their relatively large brains.  (Redford and Eisenberg 1992)

The Phyllostomus genus is found to be omnivorous, but captive P. discolor is known to feed on fruit and to refuse meat (Nowak 1999).  In Phyllostomus, pelage is clearly differentiated into fine wavy under hairs and thicker, straighter longer over hairs (Wetterer et al 2000).  The inferior border of the horseshoe is defined by a thin, free flap of skin in many phyllostomines such as Phyllostomus (Wetterer et al 2000).

Neuweiler (2000) found in eight mother-infant pairs of P. discolor, each mother’s directive calls were distinctly different, and the isolation calls of the young gradually adapted to the time-frequency structure of the mothers call.

There is a need for conservation of mammalian diversity on the extensive drylands of southern South America as they harbor more endemic species, genera, and families than the Amazon Basin.  In both central and southern South America, human land-use practices have caused considerable habitat fragmentation and desertification, which may have affected distributional limits of some mammals.  There is heightened concern about the status of the bat fauna in arid portions of the southern cone from desertification and throughout Paraguay because of increased economic development  (Willeg et al 2000).

Literature Cited:

Emmons, L. H.  1990.  Neotropical Rainforest Mammals, a field guide.  The University of Chicago Press, Chicago, Illinois.  58-59.

Koopman, K. F.  1982.  Biogeography of the bats of South America.  Pages 273-302, in Mammalian biology in South America (M. A. Mares and H. H. Genoways, eds.).  Special Publications Series, Pymatuning Laboratory of Ecology, University of Pittsburgh 6: 1-539.

Koopman, K. F.  1993.  Order Chiroptera.  Pages 137-241, in Mammalian species of the world: a taxonomic and geographic reference (D. E. Wilson and D. M. Reeder, eds.).  Smithsonian Institution Press, Washington, D.C.

Neuweiler, G.  The Biology of Bats.  2000.  Oxford University Press, New York.  258, 275-276.

Nowak, R. M.  Walker’s Mammals of the World. 6th Edition, Volume 2.  1999.  John Hopkins University Press.  362-364.

Redford, K. H. and J. F. Eisenberg.  Mammals of the Neotropics: the southern cone. Volume 2: Chile, Argentina, Uruguay, Paraguay.  1992.  The University of Chicago Press, Chicago, Illinois.

Wetterer, A. L., M. V. Rockman, and N. B. Simmons.  2000.  Phylogeny of Phyllostomid bats (Mammalia: Chiroptera): data from diverse morphological systems, sex chromosomes, and restriction site.  Bulletin of the American Museum of Natural History Number 248: 1-200.

Willeg, 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 Aimee Wiese, Biology 378 (Mammalogy), University of Wisconsin – Stevens Point.  Edited by Christopher Yahnke. Page last updated August 15, 2005.