Spiny rat

Proechimys semispinosus

SUBFAMILY

Eumysopinae

TAXONOMY

Echimys semispinosus (Tomes, 1860), Esmeraldas, Ecuador. OTHER COMMON NAMES

German: Igelratten; Spanish: Sacha cui (Peru); Surinamese: Maka alata.

PHYSICAL CHARACTERISTICS

The size of a house rat or white lab rat, but with a proportionately larger head and smaller ears. Fur (especially on the back and rump) is bristly to the touch due to the presence of stiffened, flattened hairs. Above is an orangish brown, and below is pure white. The tail is naked and is often pale toward the end. A weakness in the fifth vertebra of the tail means that, like lizards, Proechimys rats can break off the tail as distraction technique against predators. A rare recessive gene means that some "spiny" mice actually lack spiny fur.

DISTRIBUTION

Southern Honduras to coastal Colombia and Peru, only west of the Andes in South America.

HABITAT

Forest, often near waterways. Prefer dense vegetation, especially around treefalls.

I Isothrix bistriata I Proechimys semispinosus I Chaetomys subspinosus

BEHAVIOR

P. semispinosus does not dig its own burrow, but uses available depressions, including cavities in rocks, holes in logs, or burrows of other animals. This species is nocturnal, with a small home range, 0.2-3.7 acres (0.1-1.5 ha), with that of the female being smaller than the male's range. Population density fluctuates seasonally, nearly quadrupling at the end of the rainy season. There is considerable overlap in home ranges, with only burrows specifically defended, and only against members of the same species and sex. Females make a variety of birdlike twitterings to their young as they follow her around the territory.

FEEDING ECOLOGY AND DIET

Members of this family are important seed predators, eating both fallen fruit and the cached fruit of agoutis and acouchis. They also feed on fungi, including those fungi with symbiotic mycorrhizal associations with forest trees. For such fungi, they act as important dispersal agents. Members of this species will habitually take foods back to the same spot to eat them, resulting in small piles of debris that, when collected, can reveal to biologists what the animals have been eating.

REPRODUCTIVE BIOLOGY

Opportunistic breeders, these animals will breed throughout the year if conditions permit. The litter size ranges between three and six young, a large litter for an echimyid. However, in typical echimyid fashion, the young are large (birth weight 0.7 oz, or 22 g), though not as well coordinated and furred as in other genera. The estrous cycle lasts some 23 days, and gestation is 60-65 days. Weaning occurs in three to four weeks and puberty is reached in five months. Wild individuals commonly survive more than two years. Often the most numerous terrestrial mammal in a rainforest, Proechimys species provide important food sources for small carnivores such as ocelots and jaguarondis as well as for bushmasters and other snakes.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS Trapped for meat by rural residents. ♦

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