What Are Mustelids?

Global geographic range of mustelids.
Introduced range in New Zealand.

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.(1) 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(2)

► Guloninae

The fisher (Pekania pennanti), tayra (Eira barbara), wolverine (Gulo gulo), and martens.

► Helictinae

Ferret-badgers

► Ictonychinae

The striped polecat (Ictonyx striatus), Saharan striped polecat (Ictonyx libycus), marbled polecat (Vormela peregusna), African striped weasel (Poecilogale albinucha), Patagonian weasel (Lyncodon patagonicus), and grisons.

► Lutrinae

Otters

► Melinae

True badgers

► Mellivorinae

Ratel, a.k.a. honey badger (Mellivora capensis)

► Mustelinae

True weasels

► Taxidiinae

North American badger (Taxidea taxus)

For the record, not all are weasels

Most of us know what otters are, but as for badgers, martens, grisons, the 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 so-called “weasel family”, fewer than half of the approximately 70 distinct mustelid species are weasels.

Technically, true weasels comprises those belonging to the genera Mustela(3)(4) and Neogale(5) (a.k.a. subfamily: Mustelinae). For this reason, broad and overgeneralised labels that imply all mustelids are weasels can not only potentially spread harmful behavioral and psychological misconceptions about non-weasel species, they also undermine the family’s evolutionary differences.

Some have misleading common names

With the black-footed ferret (Mustela nigripes) having “ferret” in its name despite not being a true ferret (Mustela furo), the fisher (Pekania pennanti) being called a “fisher cat” when they are neither related to cats nor catch fish, the wolverine (Gulo gulo) being nicknamed a “glutton” when they are not actually gluttonous, and ferret-badgers being called… well, “ferret-badgers”, it is easy to understand why so many people unfamiliar with mustelids are confused over what they are and their nature. While we understand that these are just common names and nicknames, certain misnomers (especially when used in popular culture) have contributed to a giant confusing mess with often little to no clarity for those who seek it.

To be clear, we respect cultures and do not believe in forcing others to reform their way of speaking. However, that does not change the fact that many common names and nicknames for mustelids in English are not only confusing, they can potentially be harmful when they contribute to misinformation. While scientific names are helpful for clarity, it is unrealistic to expect the average person to pay attention to them or use them in casual conversation, especially since they are not always provided in media or arguably that memorable or pronounceable. This is why regardless of the reason a mustelid was given a particular name, on this website we feel it is important to let people know certain names can be misleading, so they can be better informed and help lesson much of the avoidable confusions.

A tip regarding “American” in mustelid common names

Whatever the opinion of what it means to be an “American”, when it comes to mustelid common names in English, it is safe to say the term usually refers to the continent of North America. This is because the American marten (Martes americana), American mink (Neogale vison), and American stoat (Mustela richardsonii) are native to both the United States and Canada, with some species like the American badger (Taxidea taxus) also being native to these countries and Mexico.

Many English-speaking people only associate the term “American” with the United States, so it can mislead some into thinking these species are exclusively native to or found in said country. Of course there would be more clarity if these species simply had “North” added to their common names to undoubtedly refer to the continent, but this is usually not the case outside of our website. However, for some reason an exception is made for Lontra canadensis, which is often called the North American river otter.

They possess anal scent glands for communication

With the exception of the sea otter (Enhydra lutris),(6) all mustelids possess well-developed anal scent glands that produce a strong-smelling secretion for sexual signaling, identification, defense, and marking territory.(7) There is a common conception that the word “Mustela” is in reference to this musky odour, when it probably more likely derives from the Latin words mus (mouse) and telum (spear).(8)

They make a range of sounds

Most mustelids are very stealthy 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 for people on social media to overgeneralise all mustelids (particularly those that are weasel-like) as “dookers”, when this is far from the case. “Dooking” refers to the chuckling vocalisation made by an excited ferret (Mustela furo). 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).

There is more on the menu than eggs, poultry, and fish

Similar to the misconception in popular culture that mice only eat cheese and bears only honey, the diet of weasels and weasel-like species is sometimes overgeneralised as only consisting of eggs, poultry, or rodents, as well as all otter species exclusively consuming fish. Many mustelids are opportunistic feeders and will eat a variety of foods depending on the season, their location, and perhaps even individual taste. The following are just a few foods certain subfamilies have been reported to consume (view our references for specific species certain foods apply to):

Melinae, Helictinae, Mellivorinae, and Taxidiinae: Amphibians, small reptiles, rodents, gastropods, invertebrates, eggs, fruits, nuts, seeds, roots, insects, mushrooms, and honey.(9)(10)(11) In the case of the ratel (Mellivora capensis), in some areas they will sometimes prey upon other small or young carnivores.(12)

Mustelinae, Ictonychinae, and Guloninae: Amphibians, small reptiles, crustaceans, invertebrates, rodents, birds, fish, moles, shrews, rabbits, hares, eggs, fruits, nuts, seeds, insects, mushrooms, honey, and sometimes other small or young carnivores.(13)(14)(15)(16)(17)(18)

Lutrinae: Amphibians, small reptiles, crustaceans, invertebrates, fish, insects, birds, and small mammals.(19)(20)

They are more than just predators

Sometimes the constant focus on the predation habits of most mustelids in various media is not only arguably monotonous, it can also lead some people to assume that these animals have it easy and are practically invincible in the wild. Often not enough attention is given to their struggles. For instance, many species are prey to a number of 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 habitat encroachment and destruction, overhunting, road traffic accidents, unregulated fur trade, and illegal trafficking. Several species are even susceptible to the canine distemper virus (CDV), which is often fatal.(21)

Most mustelids also live predominantly solitary lives, with the female being solely responsible for rising their young—boldly and tirelessly risking their lives for the many mouths that depend on them for nourishment and protection. If all the above 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 and 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.(22)

References
  1. Wund, M. 2005. Mustelidae“. (On-line), Animal Diversity Web. Accessed December 30, 2020.
  2. 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. p. 133.
  3. Koepfli, Klaus-Peter, Kerry A. Deere, Graham J. Slater, Colleen Begg, Keith Begg, Lon Grassman, Mauro Lucherini, Geraldine Veron, and Robert K. Wayne. Multigene phylogeny of the Mustelidae: resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation“. BMC biology 6.1 (2008): 10.
  4. Koepfli, Klaus-Peter, Jerry W. Dragoo, and Xiaoming Wang. The evolutionary history and molecular systematics of the Musteloidea. Biology and Conservation of Musteloids. Oxford University Press, Oxford (2017): 75-91. p. 80.
  5. Patterson, Bruce D., et al. On the nomenclature of the American clade of weasels (Carnivora: Mustelidae)“. Journal of Animal Diversity 3.2 (2021): 1-8.
  6. 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.
  7. 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.
  8. King, Carolyn M., and Roger A. Powell. The Natural History of Weasels and Stoats: Ecology, Behavior, and Management. Oxford University Press, 2006. p. 3.
  9. Shefferly, N. 1999. Taxidea taxus (On-line), Animal Diversity Web. Accessed July 22, 2020.
  10. Jackson, S. 2015. Badger Pages: The ferret badgers (Melogale spp.) Badgers.org.uk. Archived from the original on 10 September 2015. Accessed 01 September 2020.
  11. KRISTOFER M. HELGEN, NORMAN T-L. LIM, LAUREN E. HELGEN, The hog-badger is not an edentate: systematics and evolution of the genus Arctonyx (Mammalia: Mustelidae), Zoological Journal of the Linnean Society, Volume 154, Issue 2, October 2008, Pages 353–385.
  12. Hoffman, Z. 2014. “Mellivora capensis (On-line), Animal Diversity Web. Accessed July 21, 2020.
  13. Rhines, C. 2003. Martes pennanti (On-line), Animal Diversity Web. Accessed February 22, 2021.
  14. Tatara, Masaya, and Teruo Doi. “Comparative analyses on food habits of Japanese marten, Siberian weasel and leopard cat in the Tsushima islands, Japan.” Ecological research 9.1 (1994): 99-107.
  15. Hajduk, L. I. 2008. “Space use and habitat selection of long-tailed weasels (Mustela frenata) in southern Illinois”. M.S., Southern Illinois University at Carbondale.
  16. Shak, M. 2012. Martes flavigula (On-line), Animal Diversity Web. Accessed February 06, 2021.
  17. Otani, Tatsuya. “Seed dispersal by Japanese marten Martes melampus in the subalpine shrubland of northern Japan.” Ecological Research 17.1 (2002): 29-38.
  18. Youngman, Phillip M. (1990). “Mustela lutreola“, Archived 18 March 2012 at the Wayback Machine. Mammalian Species, American Society of Mammalogists, No. 362, pp. 1-3, 2 figs.
  19. Pagacz, Stanisław; Witczuk, Julia (2010). “Intensive exploitation of amphibians by Eurasian otter (Lutra lutra) in the Wolosaty stream, southeastern Poland” (PDF). Annales Zoologici Fennici. 47 (6): 403–410. doi:10.5735/086.047.0604. S2CID 83809167.
  20. Yoxon, Paul, and Grace M. Yoxon. “Otters of the world”. Whittles Publishing, 2014.
  21. Van Moll, P., et al. Distemper in wild carnivores: an epidemiological, histological and immunocytochemical study“. Veterinary microbiology 44.2-4 (1995): 193-199.
  22. 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?

Badgers | Ferret-Badgers | Fisher | Grisons | Martens | Otters | Tayra | Weasels | Wolverine