The southern river otter is found in the southern parts of Chile and western Argentina. It has a long body, a flat head with small ears, and a broad muzzle with whiskers. It has velvety dark brown hair and light or grayer underparts. Its feet are equipped with claws and webs for swimming. Adults can reach an average body length of 22 to 28 inches with a tail length of 14 to 18 inches. They can weigh up to 20 lb.
The southern river otter prefers estuaries, rivers, and lakes with fresh water for its habitat. It prefers to eat crayfish and freshwater mussels. They are primarily nocturnal and solitary. Breeding may occur in July and August, and the female gives birth to up to 4 pups after a gestation period of 60 days. Social groups are generally composed of the female and her offspring.
Population estimates are unavailable. The main cause of decline is loss of habitat and hunting for its fur. The southern river otter is also affected by pollution of wetlands, since this species requires clean water. The species is legally protected both locally and internationally.