Heteromys desmarestianus
Desmarest's spiny pocket mouse

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.

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.

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.

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.

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).

No negative impacts have been reported or discussed.

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

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.

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.