Nutria, River rat
The coypu (Myocastor coypus), otherwise known as nutria or River rat, is a large, semi-aquatic rodent. In spite of being a separate species, the animal is sometimes mistaken for a beaver or otter. These rodents are 'a boon and a bane', in the sense that they are both beneficial and detrimental. Thus, endemic to South America, these animals were introduced to the British Isles in the late 1940s. Since then, they have been farmed, playing an important role in the fur industry due to the rich and soft under-layer of their fur. In the meantime, they have destroyed thousands of acres of marshlands. Nowadays, their coat continues to be used in fur industry, though this species is notorious as a pest.
The coypu somewhat resembles a very large rat, or a beaver with a small, long, and skinny hairless tail. These animals have three sets of fur. The guard hairs on the outer coat are three inches long. They have coarse, darkish brown mid-layer fur with soft dense grey under fur, also called the nutria. Three distinguishing features are a white patch on the muzzle, webbed hind feet, and large, bright orange-yellow incisors. They have approximately 20 teeth with four large incisors that grow during the entirety of their lives. The orange discoloration is due to pigment staining from the mineral iron in the tooth enamel. Coypus have prominent whiskers on each side of their muzzle or cheek area. There is no visible distinction between male and female coypu. Both are similar in coloring and weight.
Native to South America, this species occurs from middle Bolivia and southern Brazil to Tierra del Fuego. Coypus are also found in Europe, Asia, and North America as a result of numerous escapes and liberations from fur farms. Coypus generally inhabit lowland areas with the presence of fresh water. However, populations in the Andes live at heights of up to 1,190 meters. Those in the Chonos Archipelago (Chile) may inhabit brackish and salt waters. Preferred habitats include marshes, lake edges, and sluggish streams. These animals are most commonly found along banks with emergent or abundant vegetation.
Coypus are highly sociable animals, forming family groups of 2-13 individuals, usually consisting of an adult male and multiple related females with their young. Young adult males can sometimes be solitary. These animals are neither migratory nor nomadic. They live in the same area throughout their lives. As semi-aquatic animals, coypus are able to remain underwater for over 10 minutes at a time. This species is nocturnal. Period of increased activity occurs at night, when animals swim, feed, and groom. Feeding and grooming take place in special platforms, which they construct out of vegetation. They also make burrows, where they find shelter. These dens may be either simple tunnels or a tunnel system, consisting of multiple long passages of over 15 meters as well as nesting chambers. These animals are also known to make paths through the grass, traveling around their dens within a radius of 180 meters.
Coypus are thought to have a polygynous mating system, where pairs disperse right after mating. These highly productive animals mate at any time of year. The gestation period lasts for 127-139 days, yielding a litter of up to 13 young with an average of 3-6. After giving birth, the female may mate again. Thus, she is able to produce young 3 times per year. The young are born with their fur and open eyes. They feed on maternal milk for 7-8 weeks before they leave their mother. Females reach reproductive maturity at 3 months of age, whereas males become reproductively mature a bit later - at 4 months of age. Sometimes the age of reproductive maturity may delay to up to 9 months old.
Currently, there are no notable threats to the population of Coypus.
According to IUCN, the Coypu is widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC), but its numbers are decreasing.
Consuming aquatic vegetation, these animals play an important role in the wetland ecosystem of their range. However, coypus negatively affect the ecosystem in several ways. Thus, they destroy reed swamp areas as well as eliminate certain plants from their range. In some areas, these animals have considered pest species due to attacking cultivated crops such as rice and damaging dikes and irrigation facilities with their burrows. In addition, coypus destroy nests and collect eggs of some aquatic birds, including these of endangered species.