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Ferret Population Estimates
|Introduction||Table of Content||Ferret Bibliography||Population Estimates|
|Ferret Survey||Biology and Uses||Ferret in the Wild||World Distribution|
|California's Concerns||Native Carnivores||Other Mustelidae||Tables|
A REVIEW OF NATIONAL AND CALIFORNIA
POPULATION ESTIMATES OF PET FERRETS
Ronald M. Jurek, Wildlife Biologist, Bird and Mammal Conservation Program,
Wildlife Management Division
The number of ferrets illegally owned in California has never been properly assessed, yet some pet ferret groups have routinely cited estimates of this animal's abundance in discussions about matters of legislation, wildlife conservation, and public health concerns. Since the mid 1980s, organizations promoting the legalization of ferrets for pet keeping have claimed that hundreds of thousands of illegally owned ferrets are already in California. Some groups have portrayed domestic ferrets as the "Pet of the 90s," and with numbers approaching 10 million in the United States, they claim, ferrets have now become the third most numerous or popular companion animal (or "interactive" pet) in the nation. Some ferret groups have claimed that more than a half million, and up to one million, ferrets are illegally owned in California. However, nationwide pet ownership surveys do not support these claims, indicating that approximately 800,000 pet ferrets existed in the entire nation in 1996. This implies, therefore, that in recent years, there have been fewer than--possibly far fewer than--100,000 illegally owned ferrets in California.
Reprinted from: Jurek, R.M. 1998. A review of national and California population estimates of pet ferrets. Calif. Dep. Fish and Game, Wildl. Manage. Div., Bird and Mammal Conservation Program Rep. 98-09. Sacramento, CA. 11 pp.
The pet trade began promoting the domestic ferret as a household pet in the United States in the 1970s, and pet ferrets gained popularity as progress was made in neutering young ferrets, developing veterinary care, and developing and supplying ferret foods and home accoutrements. In California--where the domestic ferret has been included under importation and ownership restrictions since 1933--Department of Food and Agriculture border check stations began detecting illegally imported ferrets in 1976. By the late 1980s, statewide interceptions of vehicles containing ferrets had reached 150-300 vehicles per year (Calif. Dep. Food and Agric. records).
For centuries, this domesticated form of the European polecat (Mustela putorius) was bred exclusively for use in hunting small animals, mainly in Europe. In the 20th century in the U.S., there has been a limited history of use of ferrets as fur-farmed animals. In recent decades, laboratories have been using ferrets as research animals in a number of medical fields, such as influenza research.
In California, fewer than 1,000 ferrets are possessed under State permits by university and medical research facilities and by animal exhibitors. The Department of Fish and Wildlife has made no attempt to estimate the number of illegal ferrets kept as pets and has had no information upon which to calculate a reasonable estimate. Also, no other California agency has made an assessment. During the past 15 years, however, advocates for legalizing ferrets as pets have routinely claimed that hundreds of thousands of California citizens own hundreds of thousands of ferrets.
A reasonable estimate of the number of illegal ferrets and owners in California would be useful to agencies and the public in assessing proposed ferret legalization, including evaluating pros and cons of ferret licensing and assessing risks to public health, animal welfare, agriculture, and wildlife.
The purpose of this paper is to summarize the pet ownership claims made by, or attributed to, the ferret producers, the pet products industry, and ferret owner groups over the past 15 years; to compare those figures with professionally run, nationwide pet ownership surveys; and to assess whether these claims and surveys could be useful for estimating how abundant this animal is in California.
The claims that have been made about the size of the ferret population in the U.S. have emanated from several national ferret organizations, including Ferret Unity and Registration Organization, American Ferret Association, and League of Independent Ferret Enthusiasts. Claims about the numbers of ferrets nationally and in California have been made primarily by two California-based ferret groups, California Domestic Ferret Association and Californians For Ferret Legalization.
Professionally conducted national pet ownership surveys have been undertaken periodically by the American Veterinary Medical Association and by the American Pet Products Manufacturers Association. These are the principal sources of data on pet ownership characteristics and trends in the U.S. They determine how many households own each type of pet, estimate how many of each type are owned, and provide useful trend information to the pet industry, veterinarians, and pet welfare organizations.
Ferret Organization Claims
According to a Ferret Unity and Registration Organization (FURO) article: "There was rather a "boom" in ferret ownership in the latter half of the 1980's, with numbers of ferrets kept in the United States reaching almost 6 million." (Shimbo, 1993).
In a January 1990 report rebutting a California Department of Health Services 1988 assessment of ferret biting cases and other health and safety issues, California Domestic Ferret Association reported: "According to the Pet Industry Joint Advisory Council, 3,750,000 Americans keep over 5,000,000 ferrets in their homes, making ferrets, after cats and dogs, the third most popular "interactive" pet in that country . . ." (California Domestic Ferret Association, 1990).
The California Domestic Ferret Association and FURO reported, "Three and a half million Americans keep over six million domestic ferrets in their homes as companion animals, making them the third most popular interactive pet in the country," based on a 1986 marketing survey by American Ferret Magazine and by "Industry figures" cited in the August 1989 issue of Pet Dealer Magazine. Elsewhere in their document, the authors stated that ". . . almost 4,000,000 people already own ferrets." They also incorporated a 'short course in ferrets', which stated, "The estimated U.S. population of ferrets in 1990 is somewhat over 5,000,000 ferrets." These authors calculated ferret numbers by "Extrapolating the figures assuming the industry standard population of 5,000,000 in all states." (Phillips and Shimbo, 1990).
By the early 1990s, estimates had grown. A Mid-Atlantic Ferret Association fact sheet stated: "Today there are an estimated 5-7 million domesticated pet ferrets in the United States. Ferrets are the third most popular companion animal." The fact sheet also reported that there were 6 million ferrets in 1988 (Hoffman, et al., undated). Later, the same organization (renamed the American Ferret Association) distributed a report on ferret-bite issues that began, "Today there are an estimated 6 to 8 million domestic pet ferrets in the United States." (Hoffman, et al., 1992).
About this time, other ferret organizations commonly cited the estimate of 6 million or so pet ferrets in the U.S., and these figures were being cited by veterinary publications, also. In a Journal of the Veterinary Medical Association article on rabies vaccines, Rupprecht et al. (1990) wrote, "From solicited state surveys, the California Domestic Ferret Association estimates that there are currently 5 to 7 million pet ferrets in approximately 4 to 5 million households nationwide." In a ferret article published in a U.S. Food and Drug Administration, Public Health Service newsletter for veterinarians, Hoffman (1991) reported, without citing a source, "Today there are an estimated six to eight million ferrets in the United States."
In the mid to late 1990s, some estimates as high as 10 million ferrets were being reported. The League of Independent Ferret Enthusiasts (L.I.F.E., 1996) reported that "Performance Foods, the largest U.S. supplier of ferret-specific foods in the U.S., estimates there are 8-10 million." However, in the same report, L.I.F.E. stated, "Pet Industry Joint Advisory Council estimated as of December 1995 there were 54.2 million dogs and five million ferrets." The latter number of ferrets is similar to that attributed by California Domestic Ferret Association (1990) to this Council five years earlier.
At the July 1997 Senate Natural Resources Committee legislative hearing on a bill intended to legalize pet ferrets in California, the representative for Californians For Ferret Legalization testified that ferrets are the third most popular pet in the country and stated that there are "7 to 8 million of them."
The national rabies information coordinator for the League of Independent Ferret Enthusiasts wrote in a California-published pet ferret magazine article (Eckart, 1998): "There are an estimated 50 million dogs and 10 million pet ferrets in the United States," and then used these figures in calculating 1992 national rates of rabies in ferrets to compare with rates in dogs.
Thus, claims by ferret organizations of the number of ferrets existing in the U.S. in the late 1980s were consistently in the range of 5 or 6 million ferrets, which expanded during the 1990s to 7 to 10 million.
National Pet Ownership Surveys
Ferret organization claims of the number of pet ferrets in the U.S. are not supported by data reported in the major national pet surveys. The nationwide number of pet ferrets reported in one recent, professionally conducted pet ownership survey is only 10 to 20 percent of the numbers claimed in the mid 1990s by ferret organizations.
AVMA U.S. Pet Ownership Survey
The American Veterinary Medical Association (AVMA) sponsored its nationwide survey of pet ownership in 1991 and in 1996 (Gehrke, 1997). The survey form used for 1991 did not specifically request information about the ferret, and participants owning ferrets had to write in their information, but the 1996 form did list the ferret specifically. Approximately 60,000 households responded in the 1996 survey.
The AVMA reported that the number of ferrets in the U.S. was 275,000 in 1991 and 791,000 in 1996 (Figure 1). The rate of ownership (percentage of households owning ferrets) increased from 0.2% in 1991 to 0.4% in 1996, with the number of ferret-owning households increasing from 189,000 in 1991 to 395,000 in 1996.
The 1996 ownership rate translates to one ferret-owning household per about 250 households. Ferret-owning households were about 1.3% as common as households owning dogs, 1.5% as common as households with cats, less than one-tenth as common as households with birds, one-fifth as common as households with rabbits, and about one-fourth as common as reptile-owning households. Compared with other companion animals in 1996, the number of households owning ferrets was 7th in order among mammals.
Also, compared with other companion mammals, ferrets were the 7th in abundance, behind (in decreasing order) cats, dogs, rabbits, horses, hamsters, and guinea pigs, but ahead of gerbils (Figure 1). Cats were 77 times--and dogs 67 times--more numerous than ferrets. The number of ferrets was 16% that of rabbits, one-twentieth that of pet birds, and less than a quarter that of reptiles.
Compared with the 1991 survey, the numbers of all companion mammal species except horses had increased by 1996. Because rabbits and ferrets were not specifically listed on the 1991 form, the rate of increase during this time may not be directly comparable with that of other companion mammals. However, these data suggest that the increase in ferrets numbers was significant.
APPMA National Pet Owners Study
The American Pet Products Manufacturers Association (APPMA), representing pet supply manufacturers and importers, have conducted National Pet Owners Surveys since 1988. Although the APPMA survey sample size is smaller than the AVMA survey, the APPMA surveys more frequently, every two years, compared with AVMA surveys at four-to-five-year intervals.
APPMA's survey in early 1996 indicated that ferrets were owned in about 6% of the 5 million households owning small animal pets, excluding cats and dogs (APPMA, 1996). Thus, approximately 300,000 households nationwide owned ferrets, a significant increase since APPMA's 1992 survey. The number of ferret-owning households was about the same as gerbil-owning households. More households owned, in decreasing order, rabbits, hamsters, and guinea pigs. In each of these respects, the APPMA survey results were quite similar to those of the AVMA (Figure 2).
Both surveys showed that nearly all types of companion mammals increased in number of animals and in number of households during the early 1990s, with the most pronounced increases being in the numbers of ferrets and ferret-owning households. These increases for the various species reflected an increasing number of U.S. households, an increasing interest in obtaining certain species, or an increase in the number of pets owned per household.
Since the mid 1980s, ferret organizations promoted legalization of ferrets as pets in states that had previously banned such ownership. Through legislation and litigation, these organizations succeeded in gaining legalization in seven states since 1985, but not in California. In the five largest of these (Georgia, New Hampshire, Utah, Michigan, and Massachussets), legalization occurred in the period from 1991 to early 1996, so nearly 10 percent of the U.S. population was able for the first time to legally obtain pet ferrets. These new markets for breeders and suppliers of ferrets may have contributed to the marked increase in ferret ownership in the early 1990s.
Ferrets are illegal for pet keeping in California and Hawaii. Also, in other states where ferret keeping is generally allowed, many cities and counties restrict or prohibit ferrets. Under-estimations of ferret numbers in the two nationwide pet surveys could arise if significant numbers of survey participants who owned ferrets in areas where they are illegal chose not report having them. U.S. residents living in areas where this animal is prohibited may represent 15% or more of the nation's population (Californians represent 12% of the U.S. population). NFO Research, Inc., the survey organization for both the APPMA and AVMA, assures its survey participants that their responses, whatever the topic in its wide array of consumer-related subjects, are kept in confidence. There is no reason to assume that the AVMA data under-represent ferret numbers (see http://www.nfor.com/nforesearch.nr_white_papers.html), but even if one would want to surmise a 20% or 25% underestimate, there still would be fewer than one million pet ferrets in the nation, based on the 1996 AVMA figures.
Literature of the pet ferret advocacy groups essentially ignores the AVMA pet population survey results. However, that survey was acknowledged in a brief statement by the League of Independent Ferret Enthusiasts (L.I.F.E., 1996) in its comparative assessment of rates of dog and ferret bites: "The 1991 AVMA (American Veterinary Medical Association) estimate of 278,000 (sic) ferrets is clearly unrealistic, since as early as 1989 the California Department of Agriculture (sic) estimated there were 275,000 in that state alone." However, as will be explained later, there was no such California estimate.
In 1985, when ferret pet-keeping was gaining national popularity, California Department of Fish and Wildlife received a report produced by the California Ferret Club--an affiliate of the Southwest Ferret Association and the International Ferret Association--which estimated the numbers of ferrets and ferret owners in California as follows: "Based on our research, we conservatively estimate the current number of ferret owners in California to be approximately 300,000, or well over 1% of the population, and increasing rapidly. This includes otherwise respectable, law-abiding citizens from all walks of life. The actual number of ferrets in the state is probably close to, if not already in excess of, one million. Based on conservative estimates of the rate of population increase, it is reasonable to project that in five years there will be approximately 4 to 5 million ferrets in the state, with the number of ferret owners somewhere between 1 and 1.5 million." (California Ferret Club, undated).
In 1988, California Department of Health Services (Constantine and Kizer, 1988), in assessing ferret biting incidents, observed that "Ferret proponents have made widely varying claims about the number of illegal pet ferrets in California (ranging from 100,000 to 500,000), and we lacked reliable figures on actual statewide numbers of either captive, stray, or feral ferrets."
The Fish and Game Press Release. California Department of Fish and Game (1989) issued a press release in March 1989 reporting on the seizure in southern California of 36 illegally owned ferrets from six people, including two founders of the Southern California Ferret Association, who were suspected of trafficking and commercial breeding of prohibited wildlife. Only the final paragraph of the Department's two-page press release mentioned ferret numbers as follows: "The Department of Food and Agriculture estimates between 250,000-500,000 ferrets are currently being held in California illegally. Fish and Game officials feel the numbers may be higher." Actually, California Department of Food and Agriculture had made no estimate of the ferret population but merely repeated some of the widely disseminated claims of ferret enthusiasts.
Reporting or repeating such rumors or claims by other parties is not a "survey" of the ferret population. Interjecting into a press release the impressions of unidentified agency officials about ferret numbers does not constitute "an estimate" by the Department of Fish and Wildlife. Nevertheless, many ferret legalization advocates portray that press release as State data. During the past decade they have commonly insinuated that the press release was the definitive source for ferret population size in California, have used it as the foundation for estimating population growth, and have cited it as evidence of how popular the ferret is in California. The numbers mentioned in that press release have been cited routinely by ferret groups and, in turn, the media, over the years. For example, according to the Pacific Research Institute (Lynch, 1996), ". . . the Department of Fish and Wildlife estimated the ferret population at upwards of 500,000 in 1989."\
Recent Ferret Organization Claims: Number of Ferret Owners
Recent figures presented by California ferret groups have ranged from 100,000 to 300,000 California owners. In December 1994 (California Domestic Ferret Association, 1994) and August 1995 (Carley, 1995a), representatives of the California Domestic Ferret Association claimed that the number of California ferret owners exceeded 100,000. On November 2, 1995, the representative for the California Domestic Ferret Association, in testimony before the California Fish and Game Commission, used the March 1989 Department of Fish and Wildlife press release as his source for data on the ferret population, and from that, he reasoned, "This probably translates into a figure of at least 200,000-300,000 ferret owners today--probably more." (Carley, 1995b).
In February 1997, Californians For Ferret Legalization claimed that there were "an estimated 250,000" ferret owners in California (Carley, 1997), and in September 1997, Californians For Ferret Legalization (1997) claimed, in reference to California, "Here, there are estimated to be some 500,000 ferrets belonging to some 200,000 owners."
Recent Ferret Organization Claims: Number of Ferrets
During 1997, Californians For Ferret Legalization (1997; Carley, 1997), California Domestic Ferret Association (1997), and Ferrets Anonymous (1997) claimed that there were, more or less, 500,000 ferrets in California, citing the 1989 CDFW press release. At the July 8, 1997 Senate Natural Resources Committee hearing on legalization of ferrets in California, the ferret legislation sponsor and supporters claimed that "there has been estimated to be about 500,000 [ferrets] in California," attributing this to an estimate of the Department of Fish and Wildlife. Recently, a Californians for Ferret Legalization advertisement in a magazine stated: "Ferrets are prohibited in California. But did you know that California is home to over 500,000 ferrets by the California Department of Fish and Wildlife's own 1989 estimate?" (Critters, USA, 1998).
Although this roughly half-million population figure has been used consistently in recent years, a recent flyer announcing a California Domestic Ferret Association-sponsored veterinary seminar in September 1998 began, "An estimated ½-1 million domestic ferrets (Mustela putorius furo) reside in California . . ."
California Ownership Rates
National pet ownership surveys by pet industry and veterinary organizations estimate pet ownership rates on the basis of the percentage of households owning each type of animal. In contrast, ferret advocates typically characterize ferret ownership in terms of the number of owners, without describing what constitutes an "owner," nor indicating the relationship of "owner" to "household." For example, Carley (1998) referred to "the estimated 250,000 people affected by the state's ferret ban," clearly distinguishing such claims from estimates based on households. So, the California ferret organizations' estimates of ownership are not comparable to the national pet surveys.
Ferret organizations in California portray the ferret as already having become an extremely popular pet, despite the ban on importation. Without providing supporting data, these groups have implied that California is among the largest, if not the largest, ferret-owning states in the nation. California Domestic Ferret Association (1997)concluded that ferret population and ownership
". . . figures give California the largest ferret population of any state in the country--legal or otherwise." A Californians for Ferret Legalization advertisement in a recent magazine stated, "Did you know that a national ferret magazine rates California among it's (sic) top three states for numbers of individual subscriptions?" (Critters, USA, 1998).
There are no data comparing the ownership rate in California with the national rate. The APPMA and AVMA national surveys provide the only reliable data available on recent ferret ownership figures for households and number of ferrets per household. Accepting the AVMA nationwide ferret population figure of 791,000 and recognizing that Californians represent 12% of the U.S. population, a hypothetical figure for the number of California ferrets can be calculated if we assume that Californians own ferrets at the same rate as the national ownership rates. This means that the ferret ownership rate (the percentage of households with ferrets) in California would have to be the same as for the nation at large, and for California ferret owners to possess, on average, the same number of ferrets per ferret-owning household as the national average (which is about 2 ferrets per ferret-owning household; AVMA, 1997). Based on these assumptions, the calculated, hypothetical number of pet ferrets in California in 1996 would be 95,000 (that is, 791,000 ferrets in the U.S. multiplied by 12%, the proportion of U.S. citizens in California) in 47,400 households (395,000 x .12). Using APPMA data, the number of ferret-owning households would be much lower.
However, the proportion of households owning ferrets in California and the per capita number of ferrets are likely to be lower than elsewhere in the nation, because the California prohibition makes it much more difficult for one to purchase or import ferrets than in other states. Also, it is relatively more difficult than in other states to obtain medical attention for ferrets, and any abandoned, stray, and confiscated ferrets suitable for adoption would be sent out of California.
The popularity of ferret pet keeping in California would have to be about five times the 1996 AVMA's national rates (of percentage of households owning ferrets and/or number of ferrets owned per household) in order to achieve a statewide population of 500,000 ferrets. Under the more likely assumptions that ferret popularity in California were either one-quarter, one-half, or three-quarters the national rate, the approximate population of ferrets would be, respectively, 24,000, 47,000, or 71,000 ferrets.
If the AVMA survey tended to underestimate nationwide ferret numbers, as discussed earlier, these calculated figures for California would have to be adjusted upward by some factor. Even generously inflating the AVMA number by an additional 20-25%, for example, would translate to a population of only 60,000 ferrets for a California ownership rate that's half of the national rate, or nearly 120,000 in the unlikely event that rates were about the same.
Until better data become available directly from California studies, the only reasonable way to quantify the illegal ferret population in California is to acknowledge that no accurate assessment is possible. However, based on available 1996 national ferret ownership rates and pet population data, there would likely be fewer than, perhaps far fewer than, 100,000 pet ferrets in California.
APPMA. 1996. 1996 national pet owners study. American Pet Products Manufacturers Association, NFO Research, Inc.
California Department of Fish and Wildlife. 1989. Press Release (March 22 and March 31, 1989). "Ferrets Rounded-up by State Game Wardens."
California Domestic Ferret Association. 1990. A business of ferrets: A rebuttal to the California Department of Health Services report of 1988. (Jan. 1990) 18 pp.
California Domestic Ferret Association. 1994. Ferret Focus, Issue #5, December 1994.
California Domestic Ferret Association. 1997. Why CDFA was formed. Web site http://www.cdfa.com/about/why.html
California Ferret Club. (undated). Why California should legalize ferrets. A report concerning the need to eliminate the prohibition of the ferret. Produced and distributed by the California Ferret Club. 7 pp. (received by CDFW Nov. 1985)
Californians for Ferret Legalization. 1997. California Update, Sep. 4, 1997, CFFL. Web site http://www.ferretnews.org/update.html
Californians for Ferret Legalization. 1998. Guide to buying and caring for small animals. Critters, USA, 1998 Annual. Vol. 3, No. 2, p. 65.
Carley, F. 1995a. California Domestic Ferret Association presentation by Floyd Carley to the California Fish and Game Commission hearing, August 1995.
Carley, F. 1995b. California Domestic Ferret Association presentation by Floyd Carley to the California Fish and Game Commission on November 2, 1995.
Carley, J. 1997. California Update, Feb. 1, 1997. Californians for Ferret Legalization. Web site http://www.ferretnews.org/update.html
Carley, J. 1998. Ferrets and the law. Ferrets USA, 1998 Annual:98-102.
Constantine, D.G., and K.W. Kizer. 1988. Pet European ferrets: A hazard to public health, small livestock and wildlife. Calif. Dep. Health Services, State of California, Sacramento, CA. 70 pp.
Eckart, T.L. (1998). Ferrets & rabies. Ferrets USA, 1998 Annual:58-61.
Ferrets Anonymous. 1997. Ferret Legalization Update, 4(1):4, Jan. 1997.
Gehrke, B.C. 1997. Results of the AVMA survey of US pet-owning household on companion animal ownership. JAVMA, Vol. 211, No. 2, July 15, 1997:169-170. [Some of the 1991 data listed in this article were incorrectly transposed in printing, so the correct numbers were verified from the U.S. Pet Ownership and Demographic Sourcebook, American Veterinary Medical Association (1997).]
Hoffman, F.A. 1991. The domestic ferret--pet of the nineties? U.S. Public Health Service, FDA Veterinarian, 6(3):1-2.
Hoffman, F.A., M. Lowery, J. Davis, M. Berbert, and S.R. Kishter. (undated). Domestic Ferret Fact Sheet. Mid-Atlantic Ferret Association. 4 pp.
Hoffman, F.A., M. Lowery, J. Davis, M. Berbert, and S.R. Kishter. 1992. The reporting and management of domestic ferret (Mustela putorius furo) bites to humans. American Ferret Association. 9 pp.
L.I.F.E. 1996. L.I.F.E. fact sheet on ferret vs dog bites. League of Independent Ferret Enthusiasts. Web site http://www.acmeferret.com.
Lynch, M. 1996. Ferreting out the facts on the California Department of Fish and Game's war on the domestic ferret. Pacific Research Institute, San Francisco. 22 pp.
Phillips, W.B., and F. Shimbo. 1990. 1990 public information manual. Calif. Domestic Ferret Association. Produced in cooperation with the Ferret Unity and Registration Organization, Inc. 135 pp.
Rupprecht, C.E., J. Gilbert, R. Pitts, K. Marshall, and H. Koprowski. 1990. Evaluation of an inactivated rabies virus vaccine in domestic ferrets. JAVMA, 196(10):1614-1616.
Shimbo, F. 1993. The ferret and the cat. The Weasel Help Monthly, FURO (November/December 1993), 6(6):21.