The word “weasel” might conjure images of slyness, but the energetic and playful ermine, also known as a stoat or short-tailed weasel, is capturing hearts with its undeniable charm. These petite carnivores, smaller than the average ferret, might seem like ideal pets due to their size and captivating nature. This sparks the question: can ermines be kept as pets, and if so, what does their care entail?
Understanding the Ermine
The ermine, scientifically known as Mustela erminea, is also commonly called the stoat or short-tailed weasel. Similar to domestic ferrets, they belong to the Mustelidae family, which includes badgers, otters, sables, and minks. Many mustelids are known for their carnivorous diets and reputations as skilled predators. The ermine is closely related to the least weasel (Mustela nivalis) and shares traits with minks, such as tree-climbing ability and proficiency in swimming [6].
Ermines range in size from about 170 to 330mm (roughly 6.7 to 13 inches) from head to tail, with males typically twice the size of females [6]. Their weight varies from approximately 25 to 116 grams [6]. Ermines are found across temperate regions of Eurasia and North America [6]. They have also established a significant presence in New Zealand after being intentionally introduced in the late 19th century, along with least weasels and ferrets, to manage rabbit populations [5]. However, in New Zealand, they are now considered invasive pests and are actively culled to protect native bird species [8][9].
Ermine Diet in the Wild
The ermine’s diet is adaptable, influenced by location, gender, prey availability, and season. In areas with human development, voles are a primary food source [2][3][4], while deer mice are common prey in boreal forests. They also regularly hunt shrews, squirrels, and chipmunks [2]. A study analyzing the stomach contents of stoats and least weasels in Great Britain revealed that lagomorphs (rabbits and hares) constituted 65% of their diet, with the remainder consisting of small rodents, birds, and eggs. Male ermines were found to consume more lagomorphs than females [7]. Their diet also includes lemmings, frogs, fish, and insects [6], showcasing their opportunistic carnivorous nature.
Legality of Ermines as Pets
In some regions, owning an ermine as a pet is legally permissible. Ermines are classified as “least concern” on the IUCN Red List, with a stable population reported as of 2021 [10]. This designation means they are not protected under endangered species laws in many areas.
However, due to their native status in many parts of the United States and other countries, keeping ermines as pets is often restricted by wildlife laws that prohibit the possession of native species. Regulations vary significantly by location. For instance, in Florida, USA, it might be legal to own an ermine with a Class 3 license, but this is an exception rather than the rule. Prospective ermine owners should thoroughly investigate local and national wildlife regulations to ascertain the legality of keeping an Ermine Pet in their specific area.
Acquiring an Ermine Pet
Ermines are not commonly found in the pet trade and are rarely, if ever, available for purchase as pets. There are primary reasons for their scarcity in the pet market.
Firstly, ermines have proven to be challenging to breed successfully in captivity [8]. Similar to minks, any potential captive population, and thus presence in the pet trade, would likely originate from fur farms with a commercial interest in breeding them. This is how captive populations of red foxes, martens, and minks were established.
Historically, ermines have been valued for their winter fur, which turns a pristine white. However, they have specific needs that complicate commercial breeding, including a preference for pre-killed or even live prey. Captivity-induced stress can also significantly reduce their reproductive success [8]. This is noteworthy because ermines are prolific breeders in their natural habitat, reaching sexual maturity very early and capable of mating even as neonates. Remarkably, there is a documented instance of a 17-day-old, blind, and still nursing female ermine successfully mating in captivity and subsequently giving birth [8][9].
Early attempts to breed ermines on fur farms yielded limited success, with some births attributed to wild-caught females already carrying delayed embryos. Ermine reproduction is unique due to a phenomenon called embryonic diapause. After fertilization, the embryo develops into a blastocyst, a fluid-filled sphere, which then ceases development and remains dormant in the uterus for 8-9 months. This embryonic diapause is not observed in other mustelids. Embryo development resumes in August, and remarkably, over 90% of wild ermines are pregnant between December and September [9].
While embryonic diapause might seem like a promising aspect for establishing captive breeding colonies [8], the reality is that even when captured ermines commonly possess blastocysts, successful implantation and birth are infrequent [9].
Minks, in contrast, breed readily in captivity. The ease of mink farming likely diminished any commercial interest in pursuing ermine farming. Intensive American mink farming began in 1925, and minks remain the dominant species in fur farming [8]. Currently, there are likely no commercial fur farms raising ermines in North America [8].
Even zoos rarely exhibit ermines, possibly due to their tendency to hide and the low breeding rates observed in zoological facilities [8]. Successful ermine breeding is most likely to occur with captive-born females [9]. Therefore, the emergence of ermines in the pet trade hinges on breeders possessing the expertise to successfully propagate wild-caught animals, a challenging endeavor.
Another significant hurdle in ermine pet ownership is their high energy levels and the difficulty in taming them [8]. In their natural habitat, ermines can travel up to 15 kilometers in a single night, with males covering larger territories than females [6]. Ermine behavior alternates between periods of intense activity and extended periods of rest [1]. They also cache surplus food to meet their high energy demands [6].
Ermine Pet Care Requirements
Like other mustelids, ermines require substantial space and environmental enrichment due to their high energy levels. Zoos and research facilities have housed ermines in enclosures of varying sizes, including cubic enclosures of 124 cm (approximately 49 inches), and more complex setups with holding areas and larger exhibit spaces (e.g., a 9.8×7.8×17.7” holding area connected to a 78.7×78.7×39.3” exhibit). Other enclosure dimensions used include 150x200x50cm, 600 cm diameter by 150 cm tall circular enclosures, 200x100x100 cm, 120 x 240 x 90 cm, and 200 x 400 x 220 cm [8].
For breeding and research purposes, one study recommended a minimum enclosure size of 150 x 100 x 60 cm (approximately 59×39.3×23.6 inches) for captive ermines [8].
Ermines are adept escape artists and necessitate secure enclosures. Aquarium-style tanks or cages constructed from materials with very small spacing are likely necessary for typical pet owners. Other materials used for ermine enclosures include 1mm gauge wire, metallic circular pens, steel weld mesh, and cages with wooden sides [8].
Enrichment is critical for ermine well-being and should include features such as a water pool for bathing, hollow logs and pipes for exploration, vegetation, and other stimulating elements commonly used for small, active carnivores. Nest boxes are also essential, as provided in professional ermine keeping facilities [8].
Ermines are naturally solitary animals and can exhibit aggression towards each other [1]. Therefore, they should be housed individually, except when breeding is intended.
A variety of diets have been successfully used for captive ermines, including commercial cat food, raw meat, and whole prey such as live or pre-killed rodents. The Minnesota Zoo achieved breeding success by feeding their ermines freshly killed mice, a change from a previous diet of canned cat food on which they did not reproduce.
Ermines are relatively unusual and more demanding to care for than some might initially assume. However, if captive breeding becomes more established, their potential as pets could increase. Even then, they would likely remain challenging pets, best suited for owners experienced with the husbandry requirements of similar species like domesticated minks, rather than typical ferret owners.
References
- Doncarlos, Michael W., Jay S. Petersen, and Ronald L. Tilson. “Captive biology of an asocial mustelid; Mustela erminea.” Zoo biology 5.4 (1986): 363-370.
- Edwards, Mark A., and Graham J. Forbes. “Food habits of ermine, Mustela erminea, in a forested landscape.” The Canadian Field-Naturalist 117.2 (2003): 245-248.
- Erlinge, Sam. “Food preference, optimal diet and reproductive output in stoats Mustela erminea in Sweden.” Oikos (1981): 303-315.
- Hellstedt, Paavo, and Heikki Henttonen. “Home range, habitat choice and activity of stoats (Mustela erminea) in a subarctic area.” Journal of Zoology 269.2 (2006): 205-212.
- King, C. M., and J. E. Moody. “The biology of the stoat (Mustela erminea) in the National Parks of New Zealand I. General introduction.” New Zealand journal of zoology 9.1 (1982): 49-55.
- Loso, H. 1999. “Mustela erminea” (On-line), Animal Diversity Web. Accessed March 02, 2021 at https://animaldiversity.org/accounts/Mustela_erminea/
- McDonald, Robbie A., Charlotte Webbon, and Stephen Harris. “The diet of stoats (Mustela erminea) and weasels (Mustela nivalis) in Great Britain.” Journal of Zoology 252.3 (2000): 363-371.
- McDonald, Robbie A., and Serge Larivière. “Captive husbandry of stoats Mustela erminea.” New Zealand Journal of Zoology 29.3 (2002): 177-186.
- O’Connor, Cheryl, et al. Stoat reproductive biology. Science & Technical Publishing, Department of Conservation, 2006.
- Reid, F., Helgen, K. & Kranz, A. 2016. Mustela erminea. The IUCN Red List of Threatened Species 2016: e.T29674A45203335. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T29674A45203335.en. Downloaded on 08 March 2021.
