Andalgalomys pearsoni - Pearson’s Chaco Mouse
Photo by Christopher Yahnke, collection of the Field Museum of Natural
Andalgalomys pearsoni is a
medium-sized mouse that has a relatively long tail. The tail is slightly hairy and bi-colored
with a pale brown dorsal surface. The
rest of the mouse is reddish-brown with strands of black hair scattered
throughout the dorsal region (Nowak and Paradiso 1999). The face is essentially the same color as the
dorsum but lacks the black hair and is outlined in an orange color (Eisenberg
and Redford 1992). The bottoms of the feet
are white with no hair or cushions. The
ears are slightly hairy and medium-sized (Nowak and Paradiso 1999). They appear dark brown on the outside with
pale edges (Anderson and Yates 2000). A. pearsoni resembles other members of
the same genus but differs in dorsal coloration. A.
olrogi has a yellowish-brown dorsum and A.
roigi has a grayish-brown dorsum
(Braun and Mares 1996). The total body length
of this species is 236 mm with a tail length of 124 mm, a hind foot length of
25 mm, and an ear length of 20 mm (Myers 1977).
The skull tends to be somewhat
slender in the tribe Phyllotini (Anderson and Yates
2000). The supraorbital
borders (which are clearly ridged) in genus Andalgalomys
are generally far apart and come together towards the back of the skull.
The temporal ridges are well-defined and tend to hang over the orbits. The zygomatic plate of Andalgalomys is slightly concave when compared to other species in
the tribe Phyllotini.
The auditory bullae are relatively large in this genus. The tooth morphology is brachydont. The penis contains preputial
glands, which are derived characteristics exclusive to the tribe Phyllotini (Tree of Life 2004).
Photo by Christopher Yahnke, collection of the
Field Museum of Natural History
species endemic to the chaco of South America, found exclusively in the
western region of Paraguay (Yahnke 1999). Other species in the Andalgalomys genus are located farther south.
breed often and have a short gestation period.
The young are tiny and numerous, with an average litter size of 5. Parental care is limited. Winter breeding is thought to occur, as
females trapped in July exhibited no signs of breeding. The males that were captured at this time
did, however, have large scrotal testes (Myers 1977).
Ecology and Behavior:
Andalgalomys pearsoni inhabit "islands" of
dry grasslands within the Chaco (Myers 1977).
There is an overall complexity to the distribution of animals in the Chaco. The Pearson's mouse is
affiliated with areas of bare soil. The
ground coverage consists of low herbaceous plants and very few woody plants.
They do not appear to choose their habitat based on a high amount of
litter. They are exclusive to the
regions of the western Chaco that are dry and sandy, possibly due to the division
of resources (food) among the various rodent populations (Yahnke 1999). A.
pearsoni feeds mainly on plant material, as do all members of the tribe Phyllotini. Arthropods are an insignificant portion of
their diet (MacDonald 2001).
A. pearsoni is a known carrier of hantavirus
pulmonary syndrome (HPS). A large
outbreak of the disease occurred in Paraguay in 1995 (Yahnke 1999). This disease is deadly to humans. It is transmitted by various means, including
through the droppings, urine or saliva of the infected rodent (National Center for Infectious Diseases 2004).
Andalgalomys was formerly included in the genus Graomys, as of its discovery in
1977. In 1978 the genus was changed to Andalgalomys
(Braun and Mares 1996). There is still
strong support for changing the mouse back to the genus Graomys (Braun and Mares 2000). DNA
evidence, however; shows that these two genuses are not the same, so the two
should not be placed in synonymy. One of
the DNA disparities is the differing number of diploids (Anderson and Yates
and T.L. Yates. 2000. A new genus and species of Phyllotine rodent from Bolivia. Journal of
Braun, J. K.,
and M. A. Mares. 1996. A new species of Phyllotine
rodent, genus Andalgalomys
(Muridae: Sigmodontinae) from Argentina. Journal of Mammalogy 77(4): 928-941.
________________________. 2000. Graomys, the genus that ate South America: a reply to Steppan and Sullivan.
Journal of Mammalogy 81(1):271-276.
Eisenberg, J. F., and K. H. Redford. 1992. Mammals of the Neotropics-The Southern Cone
Volume 2. University of Chicago Press, Chicago, Illinois.
D. 2001. Encyclopedia
of Mammals. Andromeda
Oxford Limited, New York, New York.
Myers, P. 1977. A new Phyllotine rodent
from Paraguay. Occasional
Papers of the Museum of Zoology,
University of Michigan. 676:1-7.
National Center for Infectious Diseases. 2004. http://www.cdc.gov/ncidod/diseaes/hanta/hps. (Accessed 3 December 2004).
M. and J. L. Paradiso. 1999. Walker’s Mammals of the World, 4th ed. Johns
Hopkins University Press, Baltimore,
“Tree of Life Web
Project: Phyllotini.” 2004.
http://www.tolweb.org/tree/phylogeny.html. (Accessed 3
Yahnke, C. J. 1999. Community ecology and habitat associations
of small mammals in the endemic region of Hantavirus Pulmonary Syndrome in the central
Paraguayan Chaco. Ph.D. Dissertation, Northern
Reference written by
Marisa Abrahamson, Biol 378 (Mammalogy),
University of Wisconsin – Stevens
Point: Edited by Chris Yahnke. Page last updated 7-25-05.