The Giant Otter (Pteronura brasiliensis) is an amphibious, mammalian carnivore native to South America. About the length of an adult human being, it is the longest member of the mustelidae, or weasel family, a globally successful group of predators. Unusually for a mustelid, the Giant Otter is a social species, with family groups typically supporting three to eight members. The groups are centred around a dominant breeding pair and are extremely cohesive and cooperative. Although generally peaceful, the species is territorial and aggression has been observed between groups. The Giant Otter is exclusively active during daylight hours. It is the noisiest otter species and distinct vocalizations have been documented that indicate alarm, aggressiveness, and reassurance. The Giant Otter ranges across north-central South America, although its distribution has been greatly reduced and is now discontinuous. The species was listed as endangered in 1999 and population estimates are typically below 5,000 in the wild. The Guianas are the last real stronghold for the species. Decades of poaching for its velvety pelt, peaking in the 1950s and 1960s, decimated population numbers. Habitat degradation and loss is the greatest current threat. The Giant Otter is also rare in captivity: as of 2003, only 60 animals were held.