Mustelidae

The Mustelidae (/ˌmʌˈstɛlɪdi/; from Latin mustela, weasel) are a family of carnivorous mammals, including weasels, badgers, otters, ferrets, martens, minks, and wolverines, among others. Mustelids (/ˈmʌstəlɪd/) are a diverse group and form the largest family in the order Carnivora, suborder Caniformia. Mustelidae comprises about 56–60 species across eight subfamilies. Mustelids vary greatly in size and behaviour. The least weasel can be under a foot in length, while the giant otter of Amazonian South America can measure up to 1.7 m (5 ft 7 in) and sea otters can exceed 45 kg (99 lb) in weight. The wolverine can crush bones as thick as the femur of a moose to get at the marrow, and has been seen attempting to drive bears away from their kills. The sea otter uses rocks to break open shellfish to eat. The marten is largely arboreal, while the European badger digs extensive networks of tunnels, called setts. Some mustelids have been domesticated: the ferret and the tayra are kept as pets (although the tayra requires a Dangerous Wild Animals licence in the UK), or as working animals for hunting or vermin control. Others have been important in the fur trade—the mink is often raised for its fur. As well as being one of the most species-rich families in the order Carnivora, the family Mustelidae is one of the oldest. Mustelid-like forms first appeared about 40 million years ago, roughly coinciding with the appearance of rodents. The direct ancestors of the modern mustelids first appeared about 15 million years ago. Within a large range of variation, the mustelids exhibit some common characteristics. They are typically small animals with elongated bodies, short legs, short, round ears, and thick fur. Most mustelids are solitary, nocturnal animals, and are active year-round. With the exception of the sea otter, they have anal scent glands that produce a strong-smelling secretion the animals use for sexual signaling and for marking territory. Most mustelid reproduction involves embryonic diapause. The embryo does not immediately implant in the uterus, but remains dormant for some time. No development takes place as long as the embryo remains unattached to the uterine lining. As a result, the normal gestation period is extended, sometimes up to a year. This allows the young to be born under more favorable environmental conditions. Reproduction has a large energy cost and it is to a female's benefit to have available food and mild weather. The young are more likely to survive if birth occurs after previous offspring have been weaned. Mustelids are predominantly carnivorous, although some eat vegetable matter at times. While not all mustelids share an identical dentition, they all possess teeth adapted for eating flesh, including the presence of shearing carnassials. With variation between species, the most common dental formula is 3.1.3.13.1.3.2. The martens, fisher and tayra are partially arboreal, while badgers are fossorial. A number of mustelids have aquatic lifestyles, ranging from semiaquatic minks and the several species of river otters to the fully aquatic sea otter. The sea otter is one of the few nonprimate mammals known to use a tool while foraging. It uses 'anvil' stones to crack open the shellfish that form a significant part of its diet. It is a 'keystone species', keeping its prey populations in balance so some do not outcompete the others and destroy the kelp in which they live.