The ferret (Mustela furo) is a domesticated mustelid descended from the European polecat. Despite its domestication, it is still illegal to own as a pet in some places.
The name "ferret" is derived from the Latin furittus, meaning "little thief", a likely reference to the common ferret penchant for secreting away small items. In Old English (Anglo-Saxon), the animal was called a "meard" or "mearp." The word "fyret" seems to appear in Middle English in the 14th century from the Latin, with the modern spelling of "ferret" by the 16th century.
The Greek word ἴκτις íktis, Latinized as ictis occurs in a play written by Aristophanes, The Acharnians, in 425 BC. Whether this was a reference to ferrets, polecats, or the similar Egyptian mongoose is uncertain.
A male ferret is called a hob; a female ferret is a jill. A spayed female is a sprite, a neutered male is a gib, and a vasectomised male is known as a hoblet. Ferrets under one year old are known as kits. A group of ferrets is known as a "business", or historically as a "busyness". Other purported collective nouns, including "besyness", "fesynes", "fesnyng", and "feamyng", appear in some dictionaries, but are almost certainly ghost words.
Ferrets have a typical mustelid body-shape, being long and slender. Their average length is about 50 cm (20 in) including a 13 cm (5.1 in) tail. Their pelage has various colorations including brown, black, white or mixed. They weigh between 0.7 and 2.0 kg (1.5 and 4.4 lb) and are sexually dimorphic as the males are substantially larger than females. The average gestation period is 42 days and females may have two or three litters each year. The litter size is usually between three and seven kits which are weaned after three to six weeks and become independent at three months. They become sexually mature at approximately 6 months and the average life span is 7 to 10 years. Ferrets are induced ovulators.
Ferrets spend 14–18 hours a day asleep and are most active around the hours of dawn and dusk, meaning they are crepuscular. If they are caged, they should be taken out daily to exercise and satisfy their curiosity; they need at least an hour and a place to play. Unlike their polecat ancestors, which are solitary animals, most ferrets will live happily in social groups. They are territorial, like to burrow, and prefer to sleep in an enclosed area.
Like many other mustelids, ferrets have scent glands near their anus, the secretions from which are used in scent marking. Ferrets can recognize individuals from these anal gland secretions, as well as the sex of unfamiliar individuals. Ferrets may also use urine marking for sex and individual recognition.
As with skunks, ferrets can release their anal gland secretions when startled or scared, but the smell is much less potent and dissipates rapidly. Most pet ferrets in the US are sold descented (with the anal glands removed). In many other parts of the world, including the UK and other European countries, de-scenting is considered an unnecessary mutilation.
If excited, they may perform a behavior called the "weasel war dance", characterized by frenzied sideways hops, leaps and bumping into nearby objects. Despite its common name, it is not aggressive but is a joyful invitation to play. It is often accompanied by a unique soft clucking noise, commonly referred to as "dooking". When scared, ferrets will hiss; when upset, they squeak softly.
Ferrets are obligate carnivores. The natural diet of their wild ancestors consisted of whole small prey, including meat, organs, bones, skin, feathers, and fur. Ferrets have short digestive systems and a quick metabolism, so they need to eat frequently. Prepared dry foods consisting almost entirely of meat (including high-grade cat food, although specialized ferret food is increasingly available and preferable) provide the most nutritional value. Some ferret owners feed pre-killed or live prey (such as mice and rabbits) to their ferrets to more closely mimic their natural diet. Ferret digestive tracts lack a cecum and the animal is largely unable to digest plant matter. Before much was known about ferret physiology, many breeders and pet stores recommended food like fruit in the ferret diet, but it is now known that such foods are inappropriate, and may in fact have negative consequences for ferret health. Ferrets imprint on their food at around six months old. This can make introducing new foods to an older ferret a challenge, and even simply changing brands of kibble may meet with resistance from a ferret that has never eaten the food as a kit. It is therefore advisable to expose young ferrets to as many different types and flavors of appropriate food as possible.
Ferrets have four types of teeth (the number includes maxillary (upper) and mandibular (lower) teeth) with a dental formula of 184.108.40.206/220.127.116.11:
- Twelve small incisor teeth (only 2–3 mm [3⁄32–1⁄8 in] long) located between the canines in the front of the mouth. These are used for grooming.
- Four canines used for killing prey.
- Twelve premolar teeth that the ferret uses to chew food—located at the sides of the mouth, directly behind the canines. The ferret uses these teeth to cut through flesh, using them in a scissors action to cut the meat into digestible chunks.
- Six molars (two on top and four on the bottom) at the far back of the mouth are used to crush food.
Ferrets are known to suffer from several distinct health problems. Among the most common are cancers affecting the adrenal glands, pancreas, and lymphatic system.
Adrenal disease, a growth of the adrenal glands that can be either hyperplasia or cancer, is most often diagnosed by signs like unusual hair loss, increased aggression, and difficulty urinating or defecating. Treatment options include surgery to excise the affected glands, melatonin or deslorelin implants, and hormone therapy. The causes of adrenal disease speculated to include unnatural light cycles, diets based around processed ferret foods, and prepubescent neutering. It has also been suggested that there may be a hereditary component to adrenal disease.
Insulinoma, a type of cancer of the islet cells of the pancreas, is the most common form of cancer in ferrets. It is most common in ferrets between the ages of 4 and 5 years old.
Lymphoma is the most common malignancy in ferrets. Ferret lymphosarcoma occurs in two forms -- juvenile lymphosarcoma, a fast-growing type that affects ferrets younger than two years, and adult lymphosarcoma, a slower-growing form that affects ferrets four to seven years old.
Viral diseases include canine distemper, influenza and ferret systemic coronavirus.
A high proportion of ferrets with white markings which form coat patterns known as a blaze, badger, or panda coat, such as a stripe extending from their face down the back of their head to their shoulder blades, or a fully white head, have a congenital deafness (partial or total) which is similar to Waardenburg syndrome in humans. Ferrets without white markings, but with premature graying of the coat, are also more likely to have some deafness than ferrets with solid coat colors which do not show this trait. Most albino ferrets are not deaf; if deafness does occur in an albino ferret, this may be due to an underlying white coat pattern which is obscured by the albinism.
Health problems can occur in unspayed females when not being used for breeding. Similar to domestic cats, ferrets can also suffer from hairballs and dental problems. Ferrets will also often chew on and swallow foreign objects which can lead to bowel obstruction.