The ferret (Musteia putorius furo) is a domestic pet. It is not a wild animal, though ferrets are descendants of the European polecat (weasel) and are, therefore, close relatives of skunks, mink, otters, and badgers.

There are several varieties of ferrets, based on coloration. Fitch ferrets (the most popular) are buff-colored, with black masks, feet and tails. Albino ferrets are white, with pink eyes. There is also the Siamese ferret. The female ferret is called a "jill", while the male is called a "hob". Babies are "kits".

The gestation period of ferrets is 42-44 days (average, 42 days). The average litter size is 8 (range, 2-17). Kits are born deaf, with their eyes closed. Their eyes open and they begin to hear between 3 and 5 weeks of age. Their deciduous ("temporary") teeth begin to erupt at 2 weeks of age, at which time they begin to eat solid food. Kits generally are weaned onto commercial kitten chow at 4-8 weeks of age. Kits reach their adult weight at 4 months of age. Males are typically twice the size of females, but both sexes undergo periodic weight fluctuations. it is not uncommon for the average ferret to add 30-40% of its body weight in fat deposited beneath the skin in the fall, and lose this fat the following spring. The average life span of ferrets is 9-10 years.

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Behavior

Ferrets make wonderful pets because of their engaging personalities, playful activity and fastidious nature. They can be easily trained to use a litter box because they tend to habitually urinate and defecate n the same places. Provide a low-sided litter box for easy entry and exit. More than one litter box may be necessary if the ferret has free run of the house.

There is no innate animosity between ferrets and dogs and cats, and all can usually share a household with little difficulty. However, ferrets have been known to attack pet birds, so it is advisable for owners of both to take appropriate precautions to prevent these encounters.

Ferrets are naturally inquisitive and can squeeze through very small spaces. it is important to "ferret-proof" your house before bringing your pet home. Thoroughly check every room it will inhabit, sealing all holes and openings wider that 1 inch in diameter. Make sure that all windows that may be opened have secure screens. Check the openings around plumbing, heating, and air conditioning ducts or pipes.

Some kits are small enough to squeeze under some doors. Ferrets are so small and silent that you will usually not hear them approach. They are easily stepped on when they are sleeping under a throw rug or suddenly turn up under foot. Their love of tunneling and their inherent curiosity frequently places them in potentially dangerous situations. They could very easily crawl unnoticed into your refrigerator, into the bottom broiler of a stove, through the rungs of a balcony railing, out the front door, or even end up in the washing machine with clothes under which the ferret was sleeping. Other dangers include folding sofa beds and reclining chairs. The obvious solution to avoiding accident and injury is to learn your ferret's habits and be constantly vigilant.

To help protect your ferret, especially if it is allowed free run of the house, obtain an adjustable, light-weight cat collar, the kind with elastic on one end, a small bee, and an ID tag. The bell will signal that your ferret is underfoot or has perhaps slipped out the front door. The bell also helps to warn caged birds allowed unrestricted freedom in the home that the pet ferret is nearby. Unfortunately, we have seen a number of cases of serious injury and death to pet birds caused by ferrets. The collar also indicates to unknowing neighbors (many people have no idea what a ferret is) that whatever it is, it must be someone's pet.

While ferrets are not destructive to most household items (furniture, clothing, etc.), some have a tendency to chew on soft rubber. This is especially dangerous because the pieces of tennis shoes, Barbie Doll toes, or other rubber items can become impacted in your ferret's intestines. Ingested pieces of kitchen gloves or sponges with household chemicals can also threaten your ferret's life if eaten. Latex rubber squeak toys should not be given to ferrets because they may swallow parts of them, causing intestinal obstruction.

All ferrets have an affinity for people. Some enjoy people more than others. The older a ferret is, the more mellow it is likely to become. Young kits tend to be nippy, but no more than a new kitten or puppy. They just nip with more enthusiasm. Some kits never nip at all, but most that do eventually outgrow it. Ferrets have tough skin and kits have sharp litter teeth. The roughhousing a kit may do with its littermates may not be appropriate for its owner's finger. Many new ferret owners mistake this nippiness for viciousness, even though the same behavior in a new kitten or puppy is accepted.

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Diseases

Two medical conditions of ferrets demand special mention: the ferret's extreme susceptibility to canine distemper and the unusual consequences of female ferrets coming into heat. Other medical conditions are also briefly discussed below.

Canine Distemper
Ferrets are highly susceptible to canine distemper. The initial signs of the disease appear 7-10 days after exposure to the virus and include inappetence and a tick mucus and pus-laden discharge from the eyes and nostrils. A rash commonly appears under the chin and in the groin area 10-12 days following exposure. The foot pads become greatly thickened. This disease is considered 100% fatal, with infected ferrets dying 3-3 1/2 weeks after initial exposure.

Prevention of this disease should be an absolute priority because treatment is useless. Kits should fist be vaccinated against canine distemper at 68 weeks of age (4-5 weeks of age if kits are from unvaccinated mothers). A booster vaccination is essential 2-3 weeks later. Yearly boosters are recommended thereafter.

Heat Periods
Female ferrets are seasonally polyestrus, which means they can come into heat more than once during the breeding season (March through August). They are also induced ovulators, which means ovulation occurs after copulation. The onset of heat is recognized by swelling of the external genitalia. If a ferret in heat does not engage in copulation, she will remain in heat for up to 160 days. If she is bred, the swelling of the external genitalia usually regresses to normal within 2-3 weeks after copulation.

Sustained sexual heat is dangerous and life-threatening because it usually results in bone marrow suppression. This results in severe anemia and decreases in the number of circulating white blood cells. Because of this likelihood, any female ferret not intended for breeding should be spayed at 6-8 months of age. Female ferrets in heat can be taken out of heat within about 3 weeks by injection of a specific hormone after the first 10 days of heat. Once out of heat, they can be spayed before they come back into heat (usually 40-50 days after administration of the hormone).

Feline Distemper
Researchers claim that ferrets are not susceptible to feline distemper. There are, however, reliable reports to the contrary. Consequently, the decision to vaccinate ferrets against this disease is an option for each ferret owner. However, if an individual ferret is likely to have substantial contact with cats (especially those of unknown or uncertain health status), vaccination of the ferret against feline distemper is a wise idea. The vaccine itself cannot harm the animal, and it represents "insurance". The vaccination schedule for feline distemper is the same as for canine distemper. Most veterinarians administer a combination canine distemper-feline distemper vaccine.

Rabies
Ferrets are highly susceptible to rabies and can transmit the virus. A rabies vaccine is now available for use in ferrets. Ferrets 3 months of age or older should be vaccinated, with annual boosters thereafter. Owners of vaccinated ferrets should know, however, that under certain circumstances, public health authorities may require euthanasia of vaccinated ferrets that have bitten a person.

Other Diseases
Ferrets are not susceptible to viruses that commonly produce upper respiratory disease in domestic cats, nor are they susceptible to canine hepatitis. These is no definitive evidence that ferrets are susceptible to canine Parvo-virus or feline leukemia virus; therefore, vaccination against these diseases is probably unnecessary. A few cases of lymphoma and lymphosarcoma (cancer have occurred in ferrets. Some of these ferrets tested positive for feline leukemia virus, while others tested negative. Though a cause and effect relationship cannot be proven by such a small number of cases, the possibility exists that ferrets may become infected with feline leukemia virus. Cancer can be one possible result of an infection. Some researchers believe that leukemia and related diseases among ferrets may be caused by a virus or viruses specific to ferrets.

Influenza: It is interesting to note that ferrets are susceptible to infection with several strains of human influenza virus. Signs of this illness may mimic those of canine distemper (listlessness, fever, inappetence, sneezing, nasal discharge, etc.). Unlike distemper, however, influenza usually passes within 5 days of the onset of illness, and ferrets recover. Treatment with a specific anti-influenza-A drug may be recommended. Such treatment is not recommended if bacterial infection complicates the influenza infection.

Parasitism: Most of the external parasites of domestic dogs and cats (fleas, mange mites, ear mites, etc.) can cause disease in ferrets. Less is known about the ferret's susceptibility to the more common internal parasites (roundworms, etc.) of dogs and cats. Protozoan parasites, also shared by dogs and cats (especially Giardia and Coccidia), can cause intestinal disease among ferrets. Periodic fecal examinations should be performed by your veterinarian to check for such parasites. Appropriate treatment can then be given, if warranted.

Ringworm: Ringworm (a fungal disease of the skin similar to athlete's foot) has been reported in young ferrets and may be transmitted by infected cats. As a rule of thumb, products manufactured and intended for use in and on cats (dewormers, flea products, ringworm medications, etc.) are safe and suitable for use in and on ferrets, with one exception: FLEA COLLARS SHOULD NEVER BY USED ON FERRETS.

Heartworm Disease: Ferrets are susceptible to Heartworm disease, a mosquito-transmitted illness seen mostly in dogs. Ferret owners must carefully consider the pros and cons of preventive therapy for this disease. Some ferrets may have adverse reactions to the drug used for Heartworm prevention. Further, the average ferret is very unlikely to be bitten by an infected mosquito unless it lives in an area of heavy Heartworm infection and is often exposed to mosquitoes.

Bacterial Infections: Various bacteria can produce a variety of diseases in ferrets, including botulism, tuberculosis, dysentery and abscesses and infections caused by bite wounds and other injuries. Judicious use of antibiotics is usually sufficient for treatment of most, but not all, of these conditions.

Heat Stroke: Ferrets lack sweat glands and are somewhat compromised in their ability to maintain normal body temperature in extremely warm environmental temperatures. If the temperature rises above 90 F, and if water is restricted or not available to ferrets, heat prostration is likely and death quite possible. Providing ample shade and spraying your ferret on hot days will help reduce the likelihood of this problem.

Urinary Stones: Urinary stones, either within the kidneys or urinary bladder, may cause serious problems in ferrets. Both sexes seem to be affected equally. Signs of urinary stones include blood in the urine, inability to urinate, a swollen and painful abdomen, vomiting, listlessness and inappetence. Surgery is usually necessary to correct this problem, though a special diet may eliminate certain types of stones or prevent recurrence.

Cardiomyopathy: Cardiomyopathy is a condition of the heart muscle seen in dogs, cats and ferrets. Most affected ferrets are males over 3 years of age. The cause for this condition is unknown. The muscle walls of the heart become thickened reducing the ability of the heart to pump adequate quantities of blood to the rest of the body. Signs include inappetence, fatigue, increased periods of sleep, intolerance to exercise, fainting and shortness of breath.

Cardiomyopathy is diagnosed using chest x-rays, and electrocardiogram (EKG), and echocardiography. All ferrets older than 3 years should have an EKG to screen for this disease.

Miscellaneous Problems: Tumors cause persistently low blood sugar levels, which produce weakness, depression, fainting spell, changes in behavior and convulsions.

A number of autoimmune diseases of ferrets have been identified. These types of diseases arise when the ferret's immune system begins to destroy one or more of the body's components. These diseases are usually very serious. Signs may include depression, lethargy and weakness. Veterinarians experienced in working with companion exotic animals should be consulted if this type of disease is suspected. An evaluation of the blood (and perhaps other tissues) is necessary to diagnose autoimmune disease.

Cataracts are fairly common in pet ferrets (young and old). Their significance and genetic predisposition are not fully understood.

Ferrets' nails cam become extremely sharp and should be trimmed periodically. The method used and guidelines followed are identical to those used in trimming the nails of a dog or a cat. Ferrets should not be declawed.

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For More Information

Below are the names and addresses of organizations and publications dedicated to ferrets.

California Domestic Ferret Association
P.O. Box 1868
Healdsburg, CA 95448
707-431-2277

Central Illinois Friends of Ferrets
P.O. Box 564
Urbana, IL 61801

The Ferret (Journal for veterinarians)
1014 Williamson St.
Madison, WI 53703

Ferret Fancier's Club
713 Chautauqua Court
Pittsburgh, PA 15214

Greater Chicago Ferret Association
P.O. Box 7093
Westchester, OL 60153
312-357-8682

International ferret Association
P.O. Box 522
Roanoke, VA 24003