Martens are largely arboreal, while European badgers dig extensive tunnel networks, called setts.

[6] They exhibit digitigrade or plantigrade locomotion, with five toes on each foot, enabling them to move in different ways (i.e. digging, climbing, swimming).

[8] Their dense fur, often serving as natural camouflage, undergoes seasonal changes to help them adjust to varying environmental conditions.

[6] With the exception of the sea otter[9] they have anal scent glands that produce a strong-smelling secretion the animals use for sexual signalling and marking territory.

While not all mustelids share an identical dentition, they all possess teeth adapted for eating flesh, including the presence of shearing carnassials.

Skunks were previously included as a subfamily of the mustelids, but DNA research placed them in their own separate family (Mephitidae).

[14] Several mustelids, including the mink, the sable (a type of marten), and the stoat (ermine), possess furs that are considered beautiful and valuable, so have been hunted since prehistoric times.

From the early Middle Ages, the trade in furs was of great economic importance for northern and eastern European nations with large native populations of fur-bearing mustelids, and was a major economic impetus behind Russian expansion into Siberia and French and English expansion in North America.

One species, the sea mink (Neogale macrodon) of New England and Canada, was driven to extinction by fur trappers.

Its appearance and habits are almost unknown today because no complete specimens can be found and no systematic contemporary studies were conducted.

Together with widespread hunting in California and British Columbia, the species was brought to the brink of extinction until an international moratorium came into effect in 1911.

Sea otters are vulnerable to oil spills and the indirect effects of overfishing; the black-footed ferret, a relative of the European polecat, suffers from the loss of American prairie; and wolverine populations are slowly declining because of habitat destruction and persecution.

The early mustelids appear to have undergone two rapid bursts of diversification in Eurasia, with the resulting species spreading to other continents only later.