Anatomy Tutorials

What makes a mustelid?

The word “mustelid” or “weasel” may give associations to something slender, smooth and short-legged. While it is true for some of the more well-known species, properly describing their essence can be a whole different matter, as this is a diverse family of carnivorans and omnivores whose members have adapted to a wide range of environments. This drastically affects the way these animals look and behave, so they do not really have many traits in common.

To make things more complicated, many of their traits are found in several other families within the order Carnivora in response to various types of evolution, like sharing similar ecological roles or keeping traits from an early ancestor they branched from. That is not to say they do not have any characteristics that sets them apart!

The basics

• The anatomy is shaped by curves and gives an even, soft appearance without sharp angles and transitions between body parts. There is no abdominal tuck like in canids, but a slight potbelly can occur.

• Flattened skull with a large braincase and short facial region, elongate from the side and broad on top and from the front. There is little to no dip where the forehead meets the nose bridge.

• Dark brown eyes (not including domesticated varieties or albino) that are widely spaced. All mustelids have horizontal slit pupils, except badgers and otters, which have round pupils. To give some examples, here are the eyes of the American mink (Neogale vison), here are the eyes of a Japanese marten (Martes melampus), and here are the eyes of a giant otter (Pteronura brasiliensis).

• Rounded, broad and flat ears that are widely spaced, often low-set. They are stiff and cannot move freely to express emotion, only to the side or lay against the sides of the skull.

• Short, but robust and muscular limbs.

• Broad, shovel-shaped paws that always have five, elongate digits for holding and gripping.

• Semi- to non-retractable claws on all digits, on the same level without dewclaws.

• Plantigrade to semi-plantigrade gait, with the entire or half of the sole in contact with the ground. Mustelids do not typically walk on their digits, and their heels are not placed as high as in felids and canids. No rule is without an exception, however, as it turns out from this photo hog badgers (genus Arctonyx) may be digitgrade.

• An extremely flexible spine that often gives a “hunchbacked” impression.

The niches

To fully understand mustelids, one has to be aware of the traits they have evolved in order to better function in the conditions they inhabit. This is where their resourcefulness and abilities really come into play, and help distinguishing them further from the other carnivorans.

• Weasels and polecats: Tunnel hunters (Own sheet is coming)

• Badgers: Generalist diggers (Own sheet is coming)

• Otters: Masters of the wet element (Own sheet is coming)

• Martens, fisher and tayra: Acrobats of the trees (Own sheet is coming)

• Wolverine: Vagabond of the North (Own sheet is coming)

Everything in-between

• American mink: The all-rounder (Own sheet is coming)

• Grisons: (Own sheet is coming)

• Ferret-badgers: (Own sheet is coming)

American Mink | Badgers | Ferret-Badgers | Fisher | Grisons | Martens | Otters | Polecats | Tayra | Weasels | Wolverine