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Liomys irroratusMexican spiny pocket mouse

By David Allen

Geographic Range

Liomys irroratus is found mainly in Mexico, though the species has been reported in southern Texas. It ranges from southern Texas in the United States and from southcentral Chihuahua to Oaxaca in Mexico.

Habitat

This mouse lives in dense vegetation and near rocky mountain slopes or stone fences. It has been found in the dense brush along the banks of the Rio Grande River and beside oxbow lakes, in subtropical palm forests, thickets of prickly pear cactus, and in chaparral. They build burrows that have their opening closed off by vegetation or mounds of dirt.

Physical Description

Liomys irroratus is a medium-sized mouse with rough pelage covering the upper body. The hairs are flattened with sharp points and grooves. The upper fur is dark gray with an orange tint. White fur covers the underside of the mouse except for the heel of the hind foot. The tail is covered with sparse hairs and is bicolored, brown above and white below. They possess external, fur lined, cheek pouches. The dental formula is that of a typical heteromyid rodent: I 1/1, C 0/0, PM 1/1, M 3/3. The average weight of Liomys irroratus is between 50 and 60 grams for males, and between 35 and 50 grams for females. The average total length of this species is 237 mm, with a tail length of 122 mm, and a hind foot length of 30mm.

  • Range mass
    50 to 60 g
    1.76 to 2.11 oz

Reproduction

Little is known about the breeding habits of Liomys irroratus. Litter sizes range from two to eight, with an average of four. Immature individuals are found throughout the year except for the month of May, suggesting that breeding occurs throughout the year.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual

Behavior

The Mexican Spiny Pocket Mouse is strictly nocturnal. When food is scarce this species is capable of going into a state of torpor. By dropping body temperature and slowing metabolism it is able to conserve energy and still be active if disturbed.

Communication and Perception

Food Habits

The Mexican Spiny Pocket Mouse feeds on the seeds of hackberry, mesquite, and other shrubs as well as herbaceous plants. These mice have been known to store seeds in burrows.

Economic Importance for Humans: Positive

None known.

Economic Importance for Humans: Negative

Liomys irroratus is not known to have any adverse affects on human populations.

Conservation Status

Contributors

David Allen (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

References

Davis, W., D. Schmidly. December 24, 1997. "The Mammals of Texas-Online Edition" (On-line). Accessed November 17, 1999 at http://www.nsrl.ttu.edu/tmot1/liomirro.htm.

Nowak, R. june 1999. Walker's Mammals of the World (6th Ed). John Hopkins University Press..

Whit, O. October 20, 1999. Accessed November 17, 1999 at http://www.barkingfrog.com/k-rats/hetintro.html.

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