Heteromys desmarestianusDesmarest's spiny pocket mouse

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Geographic Range

Southern Mexican states Veracruz and Oaxaca, through Central America and south to Northwest Colombia. It is usually found at medium to high elevations (up to 2400 m), but on the Caribbean coast in Costa Rica and Panama it has been found near sea level.

Habitat

It is locally common in areas of wet rainforest, but it can also be found in areas of secondary growth or seasonally dry forest. In lowlands it is usually found in mature rainforest. H. desmarestianus favors habitat with abundant palms.

Physical Description

Head and body length: 123-148 mm

Tail length: 133-196 mm

Hind foot length: 32-40 mm

Ear length: 16-20 mm

The forest spiny pocket mouse (Heteromys desmarestianus) is sexually dimorphic, with males typically weighing about one-third more than adult females. Size and weight also vary according to geographic location. They are smallest in East Panama and largest in the mountains of Costa Rica.

Heteromys desmarestianus has fur-lined, external pouches on either side of its mouth for temporarily storing and carrying food. The back, rump, and forearms are covered with stiff black-brown hair and peppered with interspersed cream-colored hairs. The sides are often paler black, and in dry lowlands some individuals may have a dusky-orange stripe on their sides. Ventral fur and feet are white. Their tail is bicolor with a black dorsal surface and a white ventral surface. The tail is sparsely haired, and usually about 20% longer than the head and body length, and may also have a white tip. Feet are long and narrow, and hind feet are naked. H. desmarestianus can be similar to other Heteromys species within some of its range, but can be differentiated by its dark forearms, hairless feet, and sparsely-haired tail.

  • Range mass
    46 to 87 g
    1.62 to 3.07 oz

Reproduction

Heteromys desmarestianus breeds year-round, but during extended dry periods some males and females may become reproductively inactive. Sexually active males have noticeably enlarged scrotal testes. Sexually active females can have up to five litters per year, with an average litter size of three and an interval between pregnancies of two months or longer. Annual survivorship probabilities are greater than 20%, and some individuals may survive up to 3 years in the wild.

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

Behavior

Heteromys desmarestianus is reportedly a good climber, but it is most often seen foraging on the ground at night in wet forests. It has a red eyeshine and moves across the forest floor in a series of hopping movements. It is usually silent, though some individuals in captivity have made low-pitched whines or chattering noises.

Populations of H. desmarestianus can reach high densities, sometimes reaching as many as 18 mice per hectare. Individual ranges are usually .08 to .20 ha in size, and ranges will often overlap extensively among sexes and age classes. Compared to Salvin's spiny pocket mouse (Liomys salvini), H. desmarestianus is reportedly more tolerant of conspecifics, and has dominance hierarchies less influenced by body size.

In the field, burrows of H. desmarestianus can be distinguished from the burrows of Peromyscus species. Most Peromyscus species dig their holes at a 45 degree angle, whereas most H. desmarestianus burrow entrances are vertical into the ground. Nests have also been found above ground in hollow logs.

Compared to other pocket mouse species (such as Liomys salvini), H. desmarestianus is less able to cope with food and water deprivation. in captivity without water, they die in as little as two days, and on a restricted diet they die after losing 20% of their body weight. In the wild, H. desmarestianus is a seed hoarder, storing seeds in burrows or in surface caches in its home range.

Communication and Perception

Food Habits

Although H. desmarestianus eats some insects and fruits, it is mainly a granivore. In Costa Rica, its diet consisted mainly of palm nuts (Socratea durissima, Euterpe macrospadix, Welfia georgii, Geonoma sp., and Iriartea gigantea), and other seeds (Meliosma sp., Pentaclethra macroloba, and Viriola sebifera).

Economic Importance for Humans: Positive

Because it is such an avid seed hoarder, H. desmarestianus is probably an important disperser of palm seeds and other large-seeded species.

Economic Importance for Humans: Negative

No negative impacts have been reported or discussed.

Conservation Status

H. desmarestianus has no special conservation status, but because it dwells in tropical forests it is negatively impacted by severe deforestation and non-forested agriculture. Currently it is still locally common in forested areas.

Other Comments

According to the research of Rogers and Schmidly (1982), Heteromys longicaudatus, H. temporalis, and H. lepturus are included in the H. desmarestianus species. Results were determined by analysis of cranial/external variation and bacula length. In Souteast Costa Rica, Rogers (1989) identified a chromosomally-different form that may be an undescribed species still included in H. desmarestianus.

Contributors

Elisabeth Witt (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.

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.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

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.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

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

tactile

uses touch to communicate

References

Fleming, T. 1983. Heteromys desmarestianus (Raton Semiespinosa, Spiny Pocket Mouse). Pp. 474-475 in D Janzen, ed. Costa Rican Natural History. Chicago: University of Chicago Press.

Fleming, T. 1974. The population ecology of two species of Costa Rican heteromyid rodents. Ecology, 55: 493-510.

Reid, F. 1997. A Field Guide to the Mammals of Central America and Southeast Mexico. New York: Oxford University Press.

Rogers, D. 1989. Evolutionary implications of chromosomal variation among spiny pocket mice, genus Heteromys (Order Rodentia). Southwestern Nat, 34: 85-100.

Rogers, D., D. Schmidly. 1982. Systematics of spiny pocket mice (genus Heteromys) of the desmarestianus species group from Mexico and northern Central America. Journal of Mammalogy, 63: 375-386.

Timm, R., D. Wilson, R. Clauson, LaVal, C. Vaughan. 1989. Mammals of the La Selva-Braulio Carrillo complex, Costa Rica. North American Fauna (US Fish and Wildlife), 75: 1-162.