What Are Mustelids?

Global geographic range of mustelids

For starters, not all are weasels

Most of us know what otters and badgers are, but as for martens, polecats, the American mink, wolverine, etc… Are all of these mustelids just weasels? Not exactly. In fact, many of these animals form their own genus and are considered distinct species in the family Mustelidae. And although this family is often loosely referred to as the “weasel family”, fewer than half of the approximately 60 distinct mustelid species are weasels. Technically, the “true” weasel family comprises mustelids belonging to the genus Mustela.(1) For this reason, broad terms that imply all mustelids are weasels can not only be misleading, but also undermine the family’s evolutionary differences.

A brief history

Mustelidae (pronounced “muh·steh·luh·dai) is the largest family within the order Carnivora, and also one of the most successful—with distribution on all continents save for Antarctica and Australia, as well as Madagascar and oceanic islands.(2) They are also among the most primitive, having been around for some 15 million years and undergone few anatomical changes from the first carnivorans that appeared about 40 million years ago. This does not by any means indicate they underdeveloped—on the contrary, through adapting to niches in a vast variety of environments, the mustelids have taken on an equally wide range of forms, while still having kept parts of the original design. Studying mustelids and how they function offers a rare glimpse into ancient times and evolution in effect.

The family Mustelidae comprises eight subfamilies(3)

► Guloninae

Martens, the fisher, tayra, and wolverine.

► Helictinae

Ferret-badgers

► Ictonychinae

Grisons, striped, Saharan striped, and marbled polecats, as well as the Patagonian and African striped weasels.

► Lutrinae

Otters

► Melinae

“True” badgers

► Mellivorinae

Honey badger

► Mustelinae

“True” weasels, and the American mink.

► Taxidiinae

American badger

Clever, feisty, and incredibly diverse

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They possess anal scent glands for communication

With the exception of the sea otter (Enhydra lutris),(4) all mustelids possess well-developed anal scent glands that produce a strong-smelling secretion for sexual signaling, identification, defense, and marking territory.(5) There is a common misbelief that the word “Mustela” is in reference to this musky odour, when it actually derives from the Latin words mus (mouse) and telum (spear).(6)

They make a range of sounds

Most mustelids are very stealth animals and rarely make noise to give their location. However, when under threat or socialising, we may hear some of their unique vocalisations. There is a tendency to stereotype all mustelids (particularly those that are weasel-like) as “dookers”, when this is far from the case. “Dooking” refers to the chucking vocalisation made by an excited domestic ferret. Other mustelids are known to make similar to considerably different types of sounds when excited, such as purring/barking (martens), zheeping/low trilling (weasels), and purring/squealing (otters).

More than just predators

We often hear mustelids being described as super predators, but where is the attention to them also being super mothers? These animals will go above and beyond to provide for their young; boldly and tirelessly risking their lives for the many mouths that depend on them for nourishment. Not only that, but they also must pass down their experience to their young, so they too will have the skills needed to survive.

Sometimes the constant focus on their predation habits can lead people to assume mustelids have it easy and are practically invincible in the wild. Fact is, many of the smaller species are prey to a number of larger predators such as wolves, bobcats, coyotes, foxes, and birds of prey, with humans in particular being the greatest threat to nearly all species when it comes to encroachment, habitat destruction, overhunting, unregulated fur trade, and illegal trafficking. Several species are also susceptible to the canine distemper virus (CDV), which is often fatal.(7) If all this was not enough, many of the smaller weasel species have both a high basal metabolic rate (BMR) and short gastrointestinal (GI) tract. So while they may be quick, efficient hunters, the trade off is that they are metabolically inefficient, and will perish if they do not eat within a few hours throughout the day.(8)

References
  1. Koepfli, Klaus-Peter, et al. “Multigene phylogeny of the Mustelidae: resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation”. BMC biology 6.1 (2008): 10.
  2. Wund, M. 2005. Mustelidae“. (On-line), Animal Diversity Web. Accessed December 30, 2020.
  3. Law, Chris J., Graham J. Slater, and Rita S. Mehta. Lineage diversity and size disparity in Musteloidea: testing patterns of adaptive radiation using molecular and fossil-based methods“. Systematic Biology 67.1 (2018): 127-144.
  4. Kenyon, Karl W. (1969). “The Sea Otter in the Eastern Pacific Ocean”. Washington, D.C.: U.S. Bureau of Sport Fisheries and Wildlife. p. 4.
  5. Hutchings, Michael R., and Piran CL White. Mustelid scent‐marking in managed ecosystems: implications for population management“. Mammal Review 30.3‐4 (2000): 157-169.
  6. King, Carolyn M., and Roger A. Powell. The Natural History of Weasels and Stoats: Ecology, Behavior, and Management. Oxford University Press, 2006. p. 3.
  7. Van Moll, P., et al. Distemper in wild carnivores: an epidemiological, histological and immunocytochemical study“. Veterinary microbiology 44.2-4 (1995): 193-199.
  8. King, Carolyn M. “The advantages and disadvantages of small size to weasels, Mustela species.” Carnivore behavior, ecology, and evolution. Springer, Boston, MA, 1989. 302-334.

What Are Mustelids?

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