Classification and Range
Ferrets are in the order Carnivora as part of the family Mustelidae, which also includes the subfamilies of badgers, martens, otters, skunks and wolverines. Ferrets are further classified under the subfamily Mustelinae and as one of 16 species in the genus Mustela, which also includes ermines, grisons, mink, polecats and weasels. There are three species of ferrets (also called polecats): the European (M. putorius), the steppe or Siberian (M. eversmanni) and the black-footed (M. nigripes).
The classification of ferrets is still not certain. The zoological record refers to these animals in a bewildering array of names, such as Putorius furo, Mustela putorius furo, Mustela putorius form. furo, Mustela furo, Putorius putorius furo and Putorius furo. Classification is further confused by scarce fossil evidence and inconclusive DNA tests of the source of domestic ferrets. Researchers believe that domestic ferrets either derived from M. putorius, M. eversmanni and/or M. nigripes, or a hybrid of any combination of these species. Due to the lack of a sufficient archaeological record for the domestic ferret, the International Commission on Zoological Nomenclature recently recommended the name for the domestic ferret to be Mustela furo. This recommendation has yet to be approved.
European polecats range throughout much of Europe and Asia; they have also been introduced in other countries, such as New Zealand and Australia. Domestic ferrets have no restrictions on their range and live throughout the world.
In the wild, European polecats live in dens created by other animals, near a source of water in temperate woodlands, grasslands and agricultural areas. Wild rabbits live in mostly dry areas near sea level with soft, sandy soil for burrowing. If they need areas of cover, they live in grassy fields or forests.
Ferrets have a long and slender body covered in soft fur. Their legs are short and tipped with unretractable claws. Strong front shoulders overlap a flexible spine and a long, thick neck. Domestic ferrets are sexually dimorphic (there are obvious physical differences between the sexes); adult males may be twice as large as adult females. The weight and coloration of ferrets vary with the season; these changes may be slight or remarkable. In preparation for the summer, they lose body fat, molt their fur (it becomes shorter or thinner) and possibly change the color of their fur. As winter approaches, ferrets gain weight, molt again (to grow longer hair) and revert to their winter coloration. The weight of males may increase as much as 40% compared to the summer weight.Humans breed domestic ferrets to produce a wide range of colors, but there are three basic color variations: dark (similar to the wild European polecat), albino (all white) and sable (tan with a dark face, legs and tail). Within the sable coloration, there are different names for the more than 30 varieties of patterns and markings, such as cinnamon, chocolate, champagne, panda, Siamese and silver.
Adult males weigh between 1 – 5.5 pounds (.45 – 2.5 kg), have a head and body length of 11.6 – 18.1 inches (29.5 – 46 cm) and have a tail length of 3.5 – 7.5 inches (9 – 19 cm). In contrast, adult females weigh between .45 – 2.25 pounds (.21 – 1.0 kg), have a head and body length of 8.1 – 15.2 inches (20.5 – 38.5 cm) and have a tail length of 2.8 – 5.5 inches (7 – 14 cm).
Life expectancy in the wild is 5 to 8 years. Domestic ferrets can live up to 14 years in captivity but 7 – 10 years is the average.
In the wild: ferrets are obligate carnivores, which means they eat a mostly carnivorous diet of other small mammals, such as rabbits, possums, hedgehogs and rodents. They also eat birds, bird eggs, reptiles, fish, amphibians and invertebrates. Wild ferrets may also eat carrion.
At the zoo: commercial ferret chow.
In the wild, European polecats mate between March and August. Polecats are photo-dependent ovulators, which means the amount of daylight and outside temperatures determine their natural breeding cycle. With sufficient daylight and warm temperatures, the female goes into estrous. Estrous normally lasts three to five days, but the female remains in estrous until she mates or up to six months. To gain access to females in estrous, males in nearby territories may compete with one another. Males that are ready to mate develop a stronger body odor while increased oil production in their skin glands causes the fur on their undersides to become oily and yellow. Once a male finds a female, they mate for 10 minutes to several hours but average time is one hour. Mating appears violent, as males grab females by the back of the neck and drag them around until they are completely limp. Polecats have very thick skin on the back of their necks and they can sustain very aggressive biting without serious injury.
Gestation lasts 38 – 44 days, with an average time of 42 days. If the first litter is lost or the litter size is small, the female may mate and give birth again in the same year. Females raise their young alone. Ten to 12 days before she gives birth, the female secludes herself and prepares the den. The female gives birth to a litter of two to 17 young (called kits), but litter size averages three to eight. At birth, the kits lack fur and teeth; their eyes are closed and they weigh just .18 – .53 ounces (5 – 15 g).
Kits grow very quickly, fed by the nutrient-rich milk of their mother. By 9 days of age, kits begin to grow hair and eventually have all their fur by 4 – 5 weeks old. A kit's eyes and ears do not open until 21 – 37 days after birth and their four permanent canines aren't fully developed until they are 47 – 56 days of age. Three to four weeks after birth, kits begin to venture out of the den. When the kits are 4 to 6 weeks old and weigh 10.6 – 17.6 ounces (300 – 500 g), the mother weans them. For the next few weeks, the female brings killed prey to her burrow for the kits to eat. This helps the kits imprint on what type of food to hunt as they grow older. At about 3 months of age, maternal protection ends. At this age, juveniles reach adult size, become more independent and leave the den. Juveniles remain together until they are around 6 months of age. Young polecats have a high mortality and many do not live past 1 year of age. Females reach sexual maturity at 6 – 12 months of age, while males mature at 8 – 12 months.
In contrast, healthy domestic ferrets may produce up to three successful litters per year with as many as 15 kits total. In years with multiple litters, the female produces more kits in the first litter of the season compared to subsequent litters. Domestic ferret kits and juveniles have similar development rates and weight as their wild counterparts.
Juveniles disperse an average of 3.1 miles (5 km) away from their birth den and begin to capture their own prey at 55 – 60 days old. Their first hunts are often unsuccessful, but by about 80 days of age, they almost always capture their prey. Polecats quickly kill their prey via a bite to its neck and are able to capture prey that weigh up to three times their own body weight.
Once they find a burrow in which to live, polecats dig additional entryways or rooms to better suit their needs. For prey that is too large to eat in one meal, polecats store it in a room of their burrow. Polecats do not urinate or defecate in their burrow; rather they use urine and stool to mark their territory. Polecats also use their well-developed anal scent glands to mark their territory and ward off intruders. As an additional marker, male polecats rub the skin oils from their abdomens or sides around the perimeter of their burrow. Domestic ferrets, like their wild counterparts, still maintain instinctive behaviors for territory marking and hunting. Polecats are mostly nocturnal, although females with young may forage during the day. They usually sleep during the day, as much as 15 – 20 hours. In the wild, polecats are solitary and territorial. Unless a female has a litter or is in estrous, polecats strongly defend their territory. In areas with high prey densities, they establish a smaller territory of 30 – 74 acres (12 – 30 ha). Areas with lower prey densities result in larger territories that range from 247 – 371 acres (100 – 150 ha) in size. If prey densities decrease, polecats will shift their home range to find more food.
Neither polecats nor domestic ferrets have a good sense of vision; they seem to be nearsighted. This is actually a helpful adaptation, because inside the dark burrow of a prey, they need to see movement rather than details. Instead of relying on sight, polecats use their sense of smell to track and kill prey. The gait of ferrets and polecats indicates how important their sense of smell is – they often walk or run with their nose on the ground. Like many other mustelids, polecats are strong swimmers and can easily cross rivers or streams to hunt in new areas.\
To defend their territory against other polecats or predators, polecats lunge, attack sideways or emit a staccato clucking sound. This display of bravado and scare tactics is also known as the "weasel war dance." If this display does not work, the polecat may hiss or snap its jaws. Polecats may also scream in fear; this scream can be very loud and high-pitched. Both polecats and ferrets emit strong-smelling secretions from their anal glands when they are excited or threatened.
Polecat or Ferret - What's the difference?
From a taxonomic viewpoint, there is essentially no difference. Both animals are currently classified in the same genus Mustela. However, it is unknown if they are actually the same species. The body size and post-cranial skeleton is also similar between ferrets and polecats. Additionally, on the genetic level, there are very few differences between the two animals. Both ferrets and European polecats have 40 chromosomes, whereas steppe polecats and black-footed ferrets have 38. However, while domestic ferrets can breed with wild polecats and produce hybrid young, this fact alone doesn't prove they are the same species. Interestingly, these hybrids are often identical in appearance to wild polecats.
Nonetheless, there are some noticeable differences between these two animals. For example, the skull shape and its base are different. The teeth of ferrets are more crowded and vary in number. There are also differences in the internal structures of the eyes and possibly in each animal's brain. There are strong distinctions in fur coloration, texture and durability. Each animal also has different abilities in balance, leaping and hearing. Wild polecats are solitary and territorial, while ferrets are social and share their space with other ferrets or other animals. Currently, researchers are undecided if the differences are due to domestication or taxonomic variance.
Although there are reports of domestic ferrets establishing populations in the wild, there are no scientifically verifiable feral populations in any mainland ecosystem. However, there are feral populations of ferrets in island ecosystems. In any case of feral populations of ferrets, humans introduced and bred them. It is doubtful that these animals descended from domestic ferrets; they are more likely hybrids. Although pet ferrets can escape, hundreds of years of selective breeding for docility and tameness often limit their ability to survive in the wild.
Strong Skeletal Structure
Polecats and ferrets are strict carnivores and their skeletal structure supports this diet. Starting with their teeth, most of them easily cut meat and some are rooted deep into the skull. Like a shark, polecats don't chew their food; instead, sharp carnassials cut the food into pieces and the polecat then swallows these pieces. Additionally, when grabbing prey, the lower jaw locks into the skull and prevents the jaw from dislocating during biting or from the force of the jaw muscles.
The rest of a polecat's skeleton is no exception to this predator's purpose. Powerful neck muscles combined with the long, flat skull give these animals tremendous gripping strength. A bony covering over their middle ear protects it and actually improves hearing. Long neck vertebrae make it easier to carry prey animals away from the ferret's feet and through tunnels. The long and supple spine allows great flexibility in changing directions while running or turning around in burrows. The spine also serves as a shock absorber during jumping or landing. At the end of their front elbows, there is an extension of bone to make the arms tougher for digging. Lastly, within the tendons that pass over joints, ferrets also usually have two bones for every digit on all four limbs. More bones within the tendons means more surface area on which muscle can attach and results in extremely strong feet.
History with Humans
Domestic ferrets have a long history with humans. It is incorrectly assumed that the Egyptians domesticated them around 5,000 years ago. Rather, these depictions on hieroglyphs are of the Egyptian mongoose (Herpestes ichneumon). Ferrets were likely first domesticated in the northern Mediterranean region centered around Greece, some 2,500 years ago. It is difficult to find specific references to ferrets in Greek literature, as writers used the same name for ferret as polecat. Nevertheless, Greek writers both commonly recognized and frequently described either animal.
As agriculture and the need for grain storage spread into Europe around 300 B.C., humans needed animals to control rodent infestations. Humans also commonly hunted rabbits for food. Humans chose to domesticate polecats because of their unique ability to easily hunt rabbits and quickly remove rodents from buildings. Given the ferret's natural ability to hunt rodents and the fact that domestic cats had not yet become a popular form of rodent control, the ferret was an obvious choice for domestication. However, as domestic cats became more common, human use of ferrets shifted from protecting grain storage to hunting rabbits. When hunting rabbits, humans put muzzles on the ferrets to prevent them from eating their prey.
By the 1200s, ferrets had spread to Germany and England, either through the expansion of the Roman Empire or with the Norman invasions. During Medieval times, more references to humans using ferrets to hunt rabbits appear in literature. Throughout the Age of Discovery, sailors kept ferrets on ships to control rodent populations. It is thought that this led to their introduction into the USA in the 1700s.
By the 1800s, ferrets became more commonly used as pets and royalty often gave them as gifts to visiting heads of state. However, in the early 1900s in the USA, humans imported thousands of ferrets to exterminate vermin that included rabbits, raccoons, gophers, rats and mice. The U.S. Department of Agriculture even promoted the use of ferrets for rodent control in barns, warehouses and granaries. With the advent of chemical control for vermin, ferrets were no longer necessary.
In more recent times, humans also bred ferrets to produce fur. In this capacity, the fur or pelt of the animal is called "fitch." Humans use fitch fur to adorn clothing and other items, as well as to make "flies" for fishing. This term (fitch) also has many other meanings: it may apply to an animal that is bred for its fur, a color pattern on ferrets that is similar to European polecats, hybrids of ferrets and polecats, or even European polecats exclusively. Even as late as the 1980s, fitch fur production was widespread; demand has recently decreased.
In the late 1960s, domestic ferrets began to gain in popularity as pets in the USA and around the world. Breeders started to create amazing combinations of fur length and color. Additionally, in recent decades, humans have used domestic ferrets for biomedical research. Laboratory ferrets have many research uses, including studies on toxicology, pharmacology, endocrinology, bacteriology and virology. Elsewhere in the world, humans still use ferrets to hunt and control rabbit populations, or to even transport cables through pipes or tunnels.
Location at the Zoo
Woodland Park Zoo's ferrets are currently kept off exhibit. Zoo staff use ferrets in various educational programs presented on zoo grounds.
By early 1900s, European polecats were almost eliminated throughout the United Kingdom, except for in Wales. Recent years have seen recovery in wild populations and European polecat populations remain stable on the continent of Europe. Therefore, polecats are neither threatened nor endangered. However, not all species of Mustela are so fortunate; at least two other species are endangered: the European mink (M. lutreola) and the black-footed ferret (M. nigripes). The black-footed ferret is considered to be the most endangered mammal in North America. It was native to the western United States but as of 1979 was declared extinct in the wild. Fortunately, many zoos have captive breeding programs to reintroduce black-footed ferrets to their native habitat.
Introduced populations of ferrets have also been difficult to manage. In the 1860s, humans that colonized New Zealand imported game animals such as rabbits. By the 1870s, with no natural predators, introduced rabbits had destroyed much of the landscape. Humans attempted to control these rabbit populations by releasing both wild polecats and domestic ferrets from 1879 - 1886. As a result, many of these introduced predators bred into a hybrid – the fitch. With no natural predators, fitch populations exploded on the two islands of New Zealand. Current fitch population is estimated at around 1,000,000 animals. Feral fitch colonies contributed to a disastrous decline in and continue to threaten many of the native bird populations, particularly ground nesting and flightless bird species. Since the onset of this decline, wildlife preservationists in New Zealand have attempted to control fitches through prey avoidance, trapping, poisoning and biological control. Integrated management of these feral populations offers the best hope for reducing their impact on native birds.
In comparison, ferrets and polecats introduced into Australia by early British settlers to control non-native rabbit populations had a much smaller impact. In Australia, fitches have many predators, such as dingoes, fox, feral cats and hawks.
How You Can Help!
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Contact Woodland Park Zoo at firstname.lastname@example.org to find out about ways you can support conservation programs at the zoo. Learn other ways you can help conserve wildlife and the habitats they require for survival by visiting our How You Can Help page.
Sources and Suggested Reading
American Ferret Association, Inc. Accessed June 10, 2008 at http://www.ferret.org/
Binghamton Zoo Species factsheet: Domestic Ferret. Accessed June 10, 2008 at http://www.rossparkzoo.com/animals/ferret.htm
Black-footed Ferret Recovery Program. Accessed October 7, 2008 at http://www.blackfootedferret.org/
Ferret Central. Accessed June 10, 2008 at http://www.ferretcentral.org/faq/history.html
McKay, James. 2002. Complete Guide to Ferrets. Swan Hill Press, Shrewsbury, UK. 160 p.
Poole, Trevor B. 1972. Some behavioural differences between the European polecat, Mustela putorius, the ferret, M. furo, and their hybrids. Journal of the Proceedings of the Zoological Society 166, London, pp 25-35.
Porter, Val and Nicholas Brown. 1990. The Complete Book of Ferrets. Pelham Books Ltd., London, UK. 192 p.
U.S. Fish & Wildlife Service Endangered Species Program: Black-footed ferret (Mustela nigripes). Accessed June 10, 2008 at http://www.fws.gov/endangered/i/a07.html