From least weasel to sea otter in one family
Mustelidae—named from Latin mustela, weasel—packs weasels, badgers, otters, polecats, martens, grisons, and wolverines into Carnivora’s largest caniform family. Least weasels can run under twenty centimetres; giant otters reach 1.7 metres and sea otters top forty-five kilograms. Forms like them appeared about forty million years ago.
Wolverines crack bones thick enough to shame larger carnivores. Humans keep tayras as pets or hunting aides where licenses allow, and mink farming fed the fur trade. Size and lifestyle scatter across continents, yet the elongate body and bold predation style rhyme.
Modern mustelids’ common ancestor dates near eighteen million years ago, after rodent radiations gave small hypercarnivores a moving feast. That deep timeline explains why the family is both old and species-rich inside Carnivora.
The family counts between 66 and 70 species. Typical members are small, with long bodies, short legs, short skulls, round ears and thick fur, and they may walk on their toes or on flat feet, with five toes per foot for digging, climbing or swimming. Most are solitary, active at night and awake all year, and their coats change with the seasons. Every species except the sea otter has anal scent glands used for sexual signalling and marking territory. Males are larger than females, and most species use delayed implantation, in which the embryo lies dormant before attaching to the uterus.
All have shearing carnassial teeth, usually 34 in total. Fishers, tayras and martens climb, badgers burrow, and the fully aquatic sea otter uses anvil stones while foraging, a rare case of tool use outside primates. A family of four black-footed ferrets eats around 250 prairie dogs a year. Skunks, once counted as mustelids, now have their own family, and look-alike mongooses belong to the cat-side branch of carnivores. Fur hunting wiped out the sea mink of New England and Canada, and the sea otter, whose fur is the densest of any animal, drove Russian expansion into Kamchatka, the Aleutians and Alaska.
Source: Mustelidae
