Speckled tree rats are vocal at night. Their loud nocturnal calls sound similar to cries of "cró, cró" or "tró, tró".
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.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Speckled tree rats are currently of Least Concern on the IUCN Red List. CITES does not list the species.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Echimys semivillosus is not known to adversely affect humans.
Speckled tree rats are of no known benefit to humanity.
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.
Ecosystem Impact: disperses seeds
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.
Plant Foods: leaves; seeds, grains, and nuts; fruit
Primary Diet: herbivore (Frugivore )
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.
Biogeographic Regions: neotropical (Native )
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.
Range elevation: 600 (high) m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest ; rainforest ; scrub forest
Other Habitat Features: riparian
The lifespan of E. semivillosus is unknown.
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.
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.
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.
Range mass: 0.190 to 0.410 kg.
Range length: 200 to 268 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
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.
Anti-predator Adaptations: cryptic
The mating systems of E. semivillosus have been insufficiently studied. The basic mating pattern of this species remains unknown.
Details on the reproduction of E. semivillosus are lacking. Other hystricognath rodents have extended gestation periods and long estrus cycles. In these animals, a delay of up to 40 days may occur between an infertile estrus and the initiation of a new pregnancy. Speckled tree rats have not been specifically studied in this regard, but it is reasonable to assume they follow the general family pattern. Average number of offspring for E. semivillosus is 2.
Breeding interval: The breeding interval of these animals is not known.
Breeding season: The breeding season for E. semivillosus has not been documented.
Range number of offspring: 1 to 7.
Average number of offspring: 2.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Female speckled tree rats birth their young in arboreal dens. The pups are protected in these dens prior to weaning. It is reasonable to assume that in this species, as in other mammals, mothers provide the offspring with food, protection, and grooming. The role of males in parental care is not known.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
