Echimys semivillosus
speckled tree rat

Echimys semivillosus is found across much of northern South America and on Margarita Island. The species occurs from about 10 to 2 degrees N latitude. (Mares and Ojeda, 1982; Nature Serve, 2004; Nowak, 2004)

Echimys semivillosus inhabits thorn, gallery, and dry deciduous forests as well as trees in the South American llanos. The species is relatively rare in the rainforest. It occurs at up to 600 m above sea level. Though it is known to replace Echimys armatus in drier regions, the species also thrives near rivers. In areas where they are common, speckled tree rats can occur at densities of up to 1 individual per 4 hectares. (Eisenberg, 1989; Emmons, 1990; Nowak, 2004)

Speckled tree rats are comparable in size to other arboreal spiny rats. Head and body length ranges from 200 to 268 mm. Tail length is 210 to 261 mm, or 80 to 120% of head and body length. Ears are 17 to 22 mm long. Height is 36 to 43 mm. Speckled tree rats can weigh anywhere from 194 to 407 g. (Emmons, 1990; Nowak, 1983)

The head, neck, and shoulders of E. semivillosus are usually gray streaked with black. Specimens from Columbia may have a white muzzle and black crown. The back is a uniform gray, flecked with numerous spines. These spines are white-tipped, and may continue down onto the gray-brown rump. Sides are light black or gray. Flatter, more flexible spines run down the shoulder and mid-back and are often completely white. The underbelly of speckled tree rats is white or pale orange in color, and may become gray across the abdomen. Young are gray or yellow-brown. They have soft fur and lack spines. (Emmons, 1990; Nowak, 1983)

Echimys semivillosus has small ears with pale patches behind and below. Whiskers are long, dense, and black. The tail has a thin covering of light brown hairs, but otherwise appears naked and scaly. It is rare to find a speckled tree rat with an intact tail. The vertebrae are unusually brittle – the fifth breaks particularly easily. Cheek-teeth are rooted and flat-crowned. Broad gray or gray-yellow feet have slightly elongated digits and prominent claws adapted to an arboreal lifestyle. (Eisenberg, 1989; Emmons, 1990; Nowak, 1983)

The lifespan of E. semivillosus is unknown. (Mares and Ojeda, 1982)

Speckled tree rats are an arboreal species. They create nests by lining hollow trunks or tree cavities with dry leaves. Two nests are often built vertically into one tree, one above the other. The nocturnal rats hide in the upper hole during the day, then come out to forage at night. Echimys semivillosus is said to slink, rather than scamper, along branches.

Nothing is known about the social behavior of these animals. (Eisenberg, 1989; Emmons, 1990; Nowak, 1983; Nowak, 2004)

Home Range

The home ranges of these animals is not known.

Speckled tree rats are vocal at night. Their loud nocturnal calls sound similar to cries of "cró, cró" or "tró, tró". (Nowak, 2004)

Although information on communication in E. semivillosus is scant, it is reasonable to assume that they are like other mammals in many regards. They likely have some forms of chemical communication, as scents are commonly used in mammals as a means of individual identification, marking of territories, and part of reproductive behavior. Tactile communication is likely to occur between mothers and their offspring as well as between mates. Visual signals, such as body posture may also be used in social communication.

Echimys semivillosus is primarily frugivorous. Little is known about the species' specific food preferences, but bananas, other fruits, grass, sugar cane, and nuts all make up part of the general diet of Echimyidae. Speckled tree rats feed mainly in the treetops but may also forage on the forest floor. They drink often. (Eisenberg, 1989; Nowak, 1983)

Speckled tree rats are visibly spined, which may act as a deterrent to predators. They also have easily fractured tails. These tails are likely to snap in a predator's grip and help the rats avoid capture. Gray, gray-yellow, or gray-brown pelage suggests camouflage within their arboreal habitat. (Emmons, 1990; Nowak, 1983)

Speckled tree rats have never been the subject of a satisfying ecological study. Various predators certainly exploit their presence, and these rats may aid in the dispersal of certain types of seeds. (Mares and Ojeda, 1982; Nowak, 1983; Nowak, 2004)

Echimys semivillosus is not known to adversely affect humans. (Mares and Ojeda, 1982; Nature Serve, 2004)

Speckled tree rats are of no known benefit to humanity. (Mares and Ojeda, 1982; Nature Serve, 2004)

Speckled tree rats are currently of Least Concern on the IUCN Red List. CITES does not list the species.