The Come Back Kid: The Black Footed Ferret Conservation Program
By: Gretchen Lloyd, Cheyenne Mountain Zoo (Colorado Springs)
The black footed ferret was listed as an endangered species in 1967. By the mid 1970’s wildlife biologists thought the species was extinct, or existed in such a small population that a natural disaster or disease would eventually eliminate them. They had already been listed as extinct in the wild in Canada in 1937.
Twenty-five years ago, ferrets were thought to be extinct in the wild. A very small colony of them was found in 1981 in Meeteese, Wyoming. That colony was followed closely. However, in 1987 it was noted that there were signs of distemper, which if not checked would wipe out the only existing remnant population of the black footed ferret.
Canine distemper and sylvatic plague are severe infectious diseases effecting both prairie dogs and ferrets. It is most often transmitted by the bite of an infected flea—a common parasite of prairie dogs. It can totally destroy an entire colony of prairie dogs or ferrets in a few weeks.
As a result of that threat, a healthy segment of the ferret population was rescued to begin a captive breeding program. However, the first group of captured ferrets all died because several were infected in the wild with distemper. This led to the discovery that this distemper was responsible for the rapid decline of the Meeteese population. At this point all remaining 18 black footed ferrets were captured, vaccinated, quarantined and sent to a captive breeding center. That is when the Black Footed Ferret Recovery Team was created more effectively to integrate expertise and resources of various parties contributing to the recovery program. This is a multi-agency conservation organization effort led by the U.S. Fish and Wildlife Service. It includes federal and state governments, zoos, and non-profit organizations. The team was created to conform to the amended Endangered Species Act of 1996. This allowed appropriate public and private agencies to become involved. So now we are celebrating this year as the 25th anniversary of the “Come Back Kid”. The goal was to establish 10 or more widely separated self-sustaining wild ferret populations in order to be able to down list the species to a “threatened” status. According to a study done in 1991 the captive population had increased to 311 animals and 49 were released into the wild. By 2000, more than 3,000 ferrets had been produced. Progress has been made but we have a long way to go when you think that there were about 800,000 ferrets in 1920.
There are 27 different agencies and non-profit organizations who are working with the U.S. Fish and Wildlife Services to save the ferret. This does not include the 6 existing breeding facilities which presently are raising ferrets to be put into the wild. These are:
U.S. Fish and Wildlife Service Facility near Carr, CO, Cheyenne Mt. Zoo at Colorado Springs, CO, Toronto Zoo, Louisville Zoo, Phoenix Zoo, and National Zoo’s Conservation Research Center in Fort Royal, Virginia.
Let’s talk about the history of the black footed ferret. It is the only native ferret known to North America. They once lived wherever prairie dog colonies thrived. This was throughout the western Great Plains from northern Mexico to southern Saskatchewan in Canada. They were from the foothills of the Rockies eastward through the grasslands of western Oklahoma, Kansas, Nebraska and the Dakotas. The ferrets are about 20 to 24 inches long, including a 5 to 6 inch black tipped tail and can weigh up to 2½ pounds. They are best recognized by the black mark over the eyes and black markings on the legs extending toward the shoulders and black tipped tails. They are a member of the weasel family—Mustelidae. The European or domestic ferret which is sold in pet stores resembles the black footed ferret but is a different species. The black footed ferret is a predator that kills and eats prairie dogs. They actually live in prairie dog towns and cannot survive for extended periods of time away from the prairie dog colonies. Because the ferrets are solitary and nocturnal they are rarely seen. And when they are seen, as noted in the picture, they are well camouflaged in the surrounding area. The male is slightly larger than the female. It is well adapted to its prairie environment. It has short legs with large front paws and claws developed for digging. The ferret’s large ears and eyes suggest it has acute hearing and eye sight. Smell is probably its most important sense for hunting prey underground and in the dark. They spend most of their time in the prairie dog holes. Few ferrets live beyond 3 years in the wild. In captivity, a female over 5 years of age rarely produces young; but can live to 8 years of age. It has many nocturnal predators such as owls, hawks, eagles, coyotes, badgers and bobcats.
They are closely associated with the western prairie. As the prairie was settled, large expanses of native grasslands were converted into farmland eliminating habitat for grassland-dependent species like the prairie dog. Researchers estimate that only one percent of the original prairie in the U. S. remains undisturbed by human activity. This loss of habitat is the primary reason that the ferret remains near the brink of extinction. The poisoning programs, initiated in the early 1900’s, decimated prairie dog colonies which left only small isolated populations. As they declined, so did the ferret. The ferret is almost entirely dependent on a plentiful supply of prairie dogs on which to get their food, 95% of their diet is prairie dogs.
The ferrets live in a prairie dog burrow during the day. A single family of four black footed ferrets eats about 250 prairie dogs each year. They cannot survive without access to large colonies of them. They use the holes exclusively for hiding, breeding and birthing. They do not dig their own holes. The range they travel is pretty much determined by the size of the prairie dog colony. It is estimated that about 100 to 150 acres are needed to support one ferret. Their territory is essentially marked by scent and excrement.
Presently, we do see some progress being made in providing good habitat for the ferret. In a book entitled Mammals of Colorado by Fitzgerald, Meaney and Armstrong published in 1994, it was stated that the population of white tailed prairie dogs that inhabit northwestern, and central Colorado have been increasing due largely to the termination of active poisoning campaigns in the late 1960’s and 1970’s.
U.S. and state agencies, in cooperation with private landowners, conservation groups, Native Americans, and North American zoos, have been actively reintroducing ferrets back into the wild since 1991. Beginning in Wyoming, reintroduction efforts have since expanded to sites in Montana, South Dakota, Arizona, Utah, Colorado and Chihuahua, Mexico. Proposed introduction sites have been identified in Canada. As of 2005 conservationists estimate a total of 400 ferrets now exist in the U.S. The recovery program calls for the establishment of 10 or more separate, self-sustaining wild populations. Biologists hope to have 1500 ferrets established in the wild by 2010 with at least 30 breeding adults in each population. Meeting this objective would allow the conservation status to be down listed from “endangered” to “threatened”.
In the wild both male and female ferrets are sexually active at one year of age. The gestation period is 41 to 45 days. Mating generally occurs in March or April. After about 7 weeks a litter of kits is born. The average litter size is 1 to 5. The inter birth interval is 1 year. It is about 3/4 grown by July when it first ventures out of the burrow. After it stops nursing, it depends on the mother for meals of meat. By late summer, the female leaves her kits in separate burrows during the day and gathers them up at night to hunt. Eventually a young ferret begins to hunt alone. By September it is independent and solitary. The peak reproductive period for ferrets lasts about 3 to 4 years. Few live beyond 3 or 4 years.
One ferret will eat 100 prairie dogs a year representing 90% to 95% of its diet. They will eat other small rodents when the opportunity presents itself. Most of the ferrets’ daytime activity is limited to a few hours following sunrise. The males are more active than females. The ferret does not hibernate, but in winter the amount of time it is active and the distances it travels decreases substantially. It will subsist on cached food.
The ferret can travel up to 5 to 7 miles using a series of jumps or a slow walk moving both forward and backward with equal speed. It is very vocal when excited and emits several loud barks interrupted by low hissing sounds. A male chatters to a female during breeding. The kits emit tiny squeaking sounds.
Going back to 1988 the U.S. Fish and Wildlife Service developed the Black footed Ferret Recovery Plan which emphasized the species preservation through natural breeding, development of assisted reproduction technology, and the establishment of multiple re-introduction sites. The objectives of the plan were (1) to maintain 240 ferrets of prime breeding age (1 to 3 years) in captivity, (2) to subdivide the captive population with a prescribed sex ratio into different locations in order to avoid a catastrophic loss at a single facility, and
(3) to develop a strategy for the reproductive program which would support captive breeding by developing artificial insemination using fresh sperm.
Our zoo began participating in the program in 1990. Dr. Della Garelle, our zoo veterinarian, is the SSP coordinator for the ferret program. Paul Marchan from the U. S. Fish and Wildlife Facility at Carr, CO is the stud book keeper for the ferret project. Our lead keeper at our zoo is Jeff Baughman.
The captive breeding program can be quite complex. For example, using newly installed high-intensity and broad spectrum lighting which mimics day length on the prairie, sets the stage for near perfect breeding conditions. Numerous assessments are then performed to determine the reproductive viability of the ferrets. To capture the birthing events, cameras are installed on the female’s nest box and 42 days later, if all goes well, the females give birth.
There is a very strict protocol where the ferrets are housed. Therefore, the building is quarantined and only those following the routine are allowed in the area. The keeper must shower and have a complete change of outer clothing before entering the area. He or she must have special boots and walk through a prepared solution. All this routine is to keep any possible germs from entering the facility. The door must be locked behind the entering individual to prevent anyone from wandering into the building.
A breeding protocol is strictly followed. It begins in September with weighing each ferret, inspecting each one, and pre-breeding exams. Pairings are made based on genetic factors and on recommendations made by the SSP at the annual SSP meeting. Genetic priorities revolve around minimizing inbreeding and maximizing use of low-mean kinship animals.
The female is released into the cage with the male, the keeper making certain they are compatible. They have to be sure the camera is functioning. If breeding does not occur, the female is taken out and placed with the next available male. After successful breeding, the female is checked to see if there is a positive sperm count. If so, the pair is kept together for 3 more days before separating permanently.
The kits nurse from birth to 90 days of age. At 21 days, the weaning process is begun, as well as the process of checking each kit for weight and any identifying marks. At 26 days, the kits are introduced to the Toronto Milliken Diet which is a meat product. Fresh food is given each feeding time. If they don’t seem interested, a freshly killed hamster is split open for them to eat. The food supply continues to increase as the kits grow. The mother is in with them to teach them how to eat the animal. The introduction of the fresh meat is at about 50 days of age.
At 60 days the kits get a chip placement behind the ear (left for females and right for males), and a vaccination. They are now getting 50 grams of prairie dog meat per kit.
At 70 to 75 days they try separating the kits from the mother to offer a live hamster to show them how to make a kill.
The ferrets continue to stay at the zoo if they are to be retained by the SSP program. Otherwise, they are sent to pre-conditioning pens, which for our zoo is the facility at Carr.
Now to tell you about the Carr Facility, which is located in northeastern Colorado just below the state line from Cheyenne, Wyoming. It is called the U.S. Fish and Wildlife Center for the Black-footed Ferret Recovery Center. The area is a wide open 40 acre area containing an open prairie where prairie dogs are seen. This facility is 2 years old. Before that time, this function was located at Sybille, Wyoming. That is now closed. About 90% of all ferrets raised in other places are sent here for the re-introduction process. Arizona and New Mexico do their own introduction, but a limited number. The kits are about 90 days old when sent here.
The building itself holds about 144 cages in 4 rooms. This is also a breeding facility with a very similar protocol to our zoo. It also is a quarantined area in the interior of the buildings. Very strict records are placed on each cage for each animal.
The outdoor enclosures where the ferrets are kept are very secure. The fence is 8 ft. high with a concrete barrier around the perimeter that is 8 feet deep. They don’t presume that any prairie dog will dig that deep. There is a covering over the top of all pens to keep out any predators. There are 48 enclosures in this complex. Beyond this is an outer fence with wire mesh under the grass cover to keep other animals from digging under to penetrate the enclosure. It is also high enough to keep out coyotes, antelope, deer, and other animals.
The pre-conditioning pens are prepared by placing a couple of prairie dogs in the enclosure to allow them to dig a burrow system for about 2 weeks. The introduction of ferrets to the wild occurs when a female and kits are placed in one of the enclosures. This may or may not be her own kits. The kits learn from watching the mother make a kill of the prairie dog.
By fall when the kits are about 90 days old they are ready for placement at various sites. The Carr facility releases about 200 ferrets a year. That is all that they have available. The sites must request to have a certain number of ferrets. One of the sites is in northwestern Colorado and part of eastern Utah called Brown’s Park. There are several in Montana and Wyoming plus a large one in southwestern South Dakota. This has been the most successful site since baby kits without chips have been noted. Carr has more requests for ferrets than they can supply. A release site must be about a thousand acres in size. There are also release sites in New Mexico and Arizona and the Sonoran Desert. These sites are largely supplied by facilities in those states. Some kits are retained at Carr for the SSP program.
There are some problems in site placements. There are a number of places in a given area that simply do not want the ferrets. The reason is they do not want to have the prairie dogs, which are necessary for a survival program. Also a site must be completely free of any sylvatic plague symptoms. The other major problem is that operational challenges at the conservation sites always exceed the available budget.
Most of the information for this program came from the following sources: the Cheyenne Mountain Zoo, the Black-footed Ferret Recovery Program, and the U.S. Dept. of Fish and Wildlife-the Black Footed Ferret Recovery Service.