1
Desiree Dahl
Mammalogy
Species Account
12/03/04
Calomys callosus
Large Vesper Mouse
Description:
Calomys callosus is the largest species in the genus Calomys. The large vesper
mouse is a generalist species. They are dark gray-brown on the dorsal surfaces and gray
on the ventral surfaces. The tail is sparsely haired and bicolored. The vesper mouse has
tan feet and large prominent ears. The total body length is 60-125 mm and the tail length
is anywhere from 30-90 mm (Nowak 1999). The tail is usually shorter than the head and
body. Their teeth are low-crowned. The chromosome number of the Calomys callosus is
2N=36, FN=48 (Bravo et al. 2001). Large vesper mice have either 8, 10 or 14 mammae
(Nowak 1999).
Distribution:
Calomys callosus is widely distributed across South America from Argentina to
eastern and southwestern Brazil and into Paraguay. They are one of the most widespread
genera of the Neotropical rodents (Brave et al. 2001).
Ontogeny and Reproduction
Females undergo post-partum estrus, which lasts for approximately 6 days. After
a 21.8 day gestation, they have a litter of 4-5 young. The offspring weigh approximately
2 grams at birth. The babies are weaned at 15-21 days, and sexual maturity is reached
when the mouse is 45-50 days old (Nowak 1999, Redford and Eisenberg 1992).
Ecology and Behavior
Calomys callosus are a nocturnal species that tend to live in montane grasslands,
brushy areas, and forest fringes (Nowak 1999). In Paraguay, the large vesper mouse is
found in palm savannas, bunchgrass meadows, and dry marshes (Redford and Eisenberg
1992). They shelter in bunchgrass, holes in the ground, rotting tree stumps, and among
rocks.
Calomys callosus are opportunistic of fire in open pasture habitats (Briani 2004).
When pasture fires occur, they are one of the first species to recolonize the area. The
vesper mouse is able to adapt their diet to include more invertebrates, which are more
readily available after a fire (Briani 2004). While the large vesper mouse is primarily an
insectivore that feeds on arthropods, they also feed on plant material.
Remarks
Calomys callous was identified as the rodent reservoir of the Machupo virus,
which causes BHF, or Hantavirus (Dragoo et al. 2002). BFH is a disease endemic to
Bolivia. Because of their unique DNA sequence, the large vesper mouse failed to
2
develop antibodies against the virus. The virus is transferred from mouse to mouse
venereally as well as through wounds sustained during intraspecific fighting (Johnson
2004). Humans contract BHF through the inhalation of aerosolized virus, bites from
infected mice, or through contact with the urine, saliva, or droppings of infected mice
(Johnson 2004).
Literature Cited
Bravo, J.S., Dragoo, J.W., Tinnin, D.S., Yates, T.L. 2001. Phylogeny and Evolution of
the Neotropical Rodent Genus Calomys: Inferences from Mitochondrial DNA
Sequence Data. Academic Press. Molecular Polygenetic and Evolution
20(2):173-184.
Briani, D. 2004. Fire and Small Mammals. Institution of Conservation Biology.
http://tools.search.yahoo.com/language/translation/translatedPage.php?tt=url&text
http%3a//www.ibcbrasil.org.br/noticias/detalhes.asp%3fcod_noticia=50&lp=pt_e
n&.intl=us. Accessed 1 December 2004).
Dragoo, J. W., Bravo, J., Layne, L. J., and Yates, T. L. 2002. Relationships within the
Calomys callosus species group based on amplified fragment length
polymorphisms. Biochemical Systematic and Ecology 31:703-713.
Johnson, K. 2004. The Discovery of Hantaan Virus: Comparative Biology and
Serendipity in a World at War. Journal of Infectious Diseases 190(9):1708-1722.
Nowak, M. 1999. Walker’s Mammals of the World, 6th Edition, Volume 2. Johns
Hopkins University Press. pp 1402-1404.
Redford, K. and J. Eisenberg. 1992. Mammals of the Neotropics the Southern Cone,
Volume 2. The University of Chicago Press. pp 278-279.
3
Figure 1. Geographic Distribution of Calomys callosus
Source:
http://www.natureserve.org/infonatura/servlet/InfoNatura?menuselect=none&sourceTem
plate=Ltabular_report.wmt&loadTemplate=Ldetail_report.wmt&selectedReport=&summ
aryView=Ltabular_report.wmt&elKey=642031&paging=home&save=true&startIndex=1
&nextStartIndex=1&reset=false&offPageSelectedElKey=642031&offPageSelectedElTy
pe=species&offPageYesNo=true&selectedIndexes=642031&menuselectfooter=none
4
Figure 2. Range map of Calomys callosus
Source:
http://www.natureserve.org/infonatura/servlet/InfoNatura?menuselect=none&sourceTem
plate=Ltabular_report.wmt&loadTemplate=Ldetail_report.wmt&selectedReport=&summ
aryView=Ltabular_report.wmt&elKey=642031&paging=home&save=true&startIndex=1
&nextStartIndex=1&reset=false&offPageSelectedElKey=642031&offPageSelectedElTy
pe=species&offPageYesNo=true&selectedIndexes=642031&menuselectfooter=none