#echimyidae

Painted Tree Rat Callistomys pictus

A rodent from the state of Bahia, Brazil. The painted tree-rat is found in the Atlantic forest. It also occurs in cocoa plantations where some native trees remain. As far as known, it is nocturnal.

Endangered

Demarest’s or Cuban Hutia (Capromys pilorides), family Echimyidae, endemic to Cuba

Paraguayan Punaré Thrichomys pachyurus

It is found in savannas and forest edges in southwestern Brazil and northern Paraguay within the cerrado ecoregion.

Noticing the Nutria

The nutria, or coypu (Myocastor coypus) is a species of rodent native to the lakes and wetlands of South America, from Bolivia to Tierra del Fuego in Chile and Argentina. It is often confused with capybara or beavers due to its size and shape; adults are typically 4-9 kg (9-20 lbs) and 40-60 cm (16-24 in) long. The fur is brown, and like its look-alikes the coypu has four large incisors that are a distinct orange color, which comes from the high amounts of iron in the enamel. M. coypus can be distinguished from other large rodents by its tail, which is long and slender-- ideal for swimming.

In addition to its thick three layers of fur, the nutria has several adaptations for a semi-aquatic life. Four of the five digits on the hind feet are webbed, and they have strong lungs that allow individuals to remain submerged for up to ten minutes. Females have nipples high on their flanks, to allow their young to suckle while they float in the water. The coypu's large teeth are used to feat on aquatic plants, as well as small animals like snails and mussels. Both the teeth and the tail are also used to deal with predators; when evading birds of prey, alligators, garfish, and other mammals the nutria will try to swim away, while the teeth can be used to deter turtles, snakes, and smaller predator fish.

In their native habitat, survival rates for M. coypus are extremely low. 80% of nutrias die within their first year, and it's rare for individuals to exceed three years of age in the wild. Males reach sexual maturity at 4 months old, while females can become sexually mature at only 3 months. Nutria are highly social, and can live in groups of 2-13 individuals, usually a large male and several mates and their litters. These groups construct platforms out of vegetation and burrows in muddy river banks- reaching up to 15 m (50 ft)-- where they mate and raise their young.

Mating occurs year-round, and it's not uncommon for a female to have 2 or 3 litters in a year. Gestation of a litter lasts about 130 days, after which she gives birth to an average of 5-7 young, though it may be as many as 14. Baby coypu are born with their eyes open, and can swim and feed on vegetation only hours after birth. These pups only remain with her for 4-8 weeks, after which they are weaned and either join the group as adults or leave to find another colony. This allows their mother to prepare herself for another litter-- an important task, as she is ready to become pregnant again the day after giving birth.

Conservation status: The IUCN has yet to rate the nutria, although studies have suggested they're disappearing from their native rivers and lakes. Conversely, M. coypus is highly invasive in parts of North America, Europe, Asia, and Africa, where it has been introduced by fur ranchers.

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Photos

Greg Lasley via iNaturalist

Petar Milošević via Wikipedia

Coypu (Myocastor coypus)

A young nutria rat at the Mönchbruch nature reserve in Kelsterbach, western Germany

Photograph: Dorothee Barth/DP/AFP/Getty

Speckled Tree Rat Pattonomys semivillosus

It is found in northern Colombia and Venezuela. It can be found in gallery forest and dry forest. Its diet includes fruit and seeds.