Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part IX: Breeding Season

Bunting’s kits are now at the 55 day mark.  At this stage they have the adult color pattern, but still have a juvenile appearance. This period is critical as it is when they get their first canine distemper vaccination.  Canine distemper is one of the diseases that nearly brought the black footed ferrets (BFFs) to extinction.  A special recombinant canine distemper vaccine was developed for BFFs as well as the domestic ferret. 

Bunting’s kit getting it’s first

canine distemper vaccination at

55 days of age.

The catch cage is always used now whenever they need to be examined or restrained along with thick leather bite gloves to block their escape from the catch cage. Roughly seven days from the distemper vaccination or at around 62 days old, they are anesthetized for a physical examination by one of our veterinarians.  They look for any possible abnormalities and implant a microchip under the skin for permanent identification.  

Bunting’s kit under gas anesthesia

for exam and microchip implant at

65 days of age.

Half inch long microchip

used to permanently ID the BFFs.

The microchip provides a 9 digit number

that is unique to that particular individual.

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part VIII: Breeding Season

Bunting’s kits are now growing very fast.  They are still nursing, but are mostly eating specially developed ground meat and rodents.  They are also busy playing which is important for them to strengthen and develop their motor skills. 

They are now venturing into the black tube that leads from their nestbox to the upper enclosure.  This makes getting a visual or catching the ferret to weigh extremely challenging.  They are not yet at the biting age, but very soon we will need to wear thick leather gloves to protect our hands. Since this is a reintroduction program, it is important for the kits to remain wary of humans.  Talking is kept to a minimum and handling is only done when absolutely necessary.  Once old enough, a catch cage will be used as they are too feisty and strong to hold otherwise. 

Bunting’s kits at 40 days old

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part VII: Breeding Season

Black-footed ferret (BFF) kits grow very fast.  At birth they can weigh as little as 5 grams, the same weight of a US nickel! The nest box is cleaned once at 4 days old and then a daily cleaning of the nest box resumes when the kits are 9 days old. The dams are very reluctant to leave their kits, so we usually clean them right before feeding time. The meat ball sometimes entices the dam to go to the upper enclosure long enough to close the shift slider of the nest box. We quickly clean the latrine side of the nest box.  Take a quick peek at the kits on the nest side and then let the dams back to their kits.  This allows us the opportunity to check on the kits and make sure they are looking good.

Bunting’s litter at 4 days of age.

Bunting’s litter at 9 days of age.

While Bunting’s litter continues to grow, other expectant females are due.  Over the next several weeks more litters are born.  Of the 11 SSP females 7 whelped, including the female that was given hormones to ovulate. It is extremely rare for this to be successful.  We also had 2 additional litters that belong to two 5 year olds which is also not common.  In total we had 34 kits born! This is currently a record number of BFF births for Cheyenne Mountain Zoo.  For reasons unknown, we had 6 kits that did not make it past their first day (including two of Bunting’s litter).  However, the remaining 28 kits continue to thrive.

Bunting’s kits have reached the 21 day mark.  This is when we determine the sex of the kits and begin to weigh them weekly. All 4 of them are BOYS! Their weights range from 124-130 grams which is above average for 21 day old males.  At 23 days of age they are introduced to small carnivore meat.  Their eyes are still not opened, but they do have deciduous “baby” teeth.  They often do not eat the first few days, but are observed smelling the meat.

Bunting’s kits being introduced

to meat at 23 days of age.

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part VI: Breeding Season

After 72 hours of being together, the black-footed ferret (BFF) female is separated from the male and she is returned to her enclosure.  Four days after separation, she is given her final vaginal flush for the year.  This check is to see if she has been induced to ovulate.  If she has, then her epithelial cells will look as they did at the beginning of her estrus cycle, obvious nuclei and very few cells with orange stain.  If she has not ovulated then they will look as they did before pairing, no nuclei and many orange keratinized cells. The female is re-paired immediately with a male if she has not ovulated and will sometimes be given hormones if she will not ovulate after a few pairings.  Once ovulation occurs, the females are disturbed as little as possible. 

           

The gestation or pregnancy period for BFFs is 42 days.  The diet is increased every two weeks and is almost doubled by the time she is due.  An infra-red video camera is installed on the nest box and we wait with anticipation for the kits to be born. BFF gestation period is almost like clockwork.  Most of our births occur right on the 42nd day and even near the time when the male and female were put together for breeding.  If we paired them in the morning, then the kits will usually be born in the morning.  If we paired them later in the day, then they will be born later that evening.  Since we have numerous female BFFs, a whelping calendar is created so we can keep track of all the due dates. 

For 2011, 11 SSP females were paired and 4 additional females that were non-releasable but over the age of four.  The additional 4 older females are not included in our primary breeding numbers as they are not as likely to produce kits.   One of our SSP females did not ovulate after 2 breeding attempts so she was given a hormone injection which did cause her to finally ovulate.   The remaining females that were bred and ovulated had no other issues during their gestation periods.

           

Bunting’s 4 healthy kits on camera while 

she is away getting a drink of water. 

Our first due date was on May 21st and our last was on June 22nd. On May 21st a litter of 6 kits were born!!!  Bunting Studbook #6376 is the dam (mother).  She came to Cheyenne Mountain Zoo in 2009 as a one year old and unfortunately did not produce kits in 2010.  This year, however she proved otherwise.  For reasons unknown, only 4 of the kits visible on the camera were moving.  As we do not want to jeopardize the well being of the entire litter, we generally do not interfere and let the dams take care of the deceased kits as nature would intend. The four remaining kits looked as healthy as ever and now Bunting has a lot of work ahead of her as a new mom. 

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part V: Breeding Season

The female black-footed ferrets (BFFs) come into estrus starting around March. They are checked weekly for signs of vulvar swelling. Once they are at a certain size, then vaginal washes are conducted. This allows for us to look at the epithelial cells to determine when she is at peak estrus. Samples are collected twice per week until she is ready for breeding.

The slides are stained using the Pap staining technique, which causes the cells to be different colors according to the level of estrus. In the early stages, the cells are round and have a very apparent nucleus. When she is near peak estrus, then the cells become more jagged, turn orange, and don’t have a nucleus. Once the female has 90% of the orange keratinized cells, then she is almost ready for breeding.

Peak Estrus

Early Estrus

An average years number of slides

The female is usually given 5-7 days to allow her to be at full estrus and then she is paired with a male. The males are selected using a Mate Suitability Index 1-6 (1 being excellent and 6 being very bad). This number comes from the inbreeding coefficient, mean kinship, and other genetic values of both animals. It is at this time when things start to get a little tricky. Our female is now ready, but what about the male? Is his sperm count above the 250 million per milliliter? Is he currently paired with a different female? Luckily our studbook keeper and genetic advisor have given optional backup pairing suggestions for when problems like this may occur, or if the male is busy being paired with a different female.

Once all is ready, the female is placed in the male’s enclosure. A camera is placed on the nest box to watch for breeding activity. These are normally solitary animals and if they are placed together at the wrong time, then one of them might be very aggressive toward the other. Usually our science has led us to the correct timing and the breeding goes smoothly. After about 30 minutes, the female is removed to do a vaginal wash. She is placed back quickly and the breeding continues. This wash is to check and see if there is sperm present. The challenge of this check is that there are often only a few sperm that are usually missing tails and there are a lot of other cells on the slide. It is almost like playing Where’s Waldo, but looking for a single sperm head. This can sometimes take over an hour of constant searching on the microscope. If there is no sperm found, then the female is re-paired but with a different male.

Power 10

Power 40

Digital Picture zoomed: a single sperm head

This step is important because BFFs females are induced ovulators. This means that the process of breeding will cause her to ovulate regardless of if there are sperm present. BFFs only come into estrus one time per year so if she ovulates and there are no sperm, then she may become pseudo pregnant. The female will then show all the signs of pregnancy and can even have a false birth and lactate, but no litter is produced. If this happens, then we have to wait an entire year before she can be bred again. BFFs are reproductive from the age of 1-4 for females. They only have 4 chances to reproduce, so we must make each year count.

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part IV: Beginning of Breeding Season

Due to the Black-Footed Ferrets (BFFs) having a small founding population, it is important to maintain genetic diversity as much as possible. In order to do this, BFFs must be moved between breeding facilities so we are not repeatedly breeding the same pairs of ferrets year after year. The BFF Species Survival Plan (SSP) has a genetic advisor and studbook keeper, both use a computer program to decide what animals should be paired. Once these recommendations are made, the animals are transferred as needed. In order to reduce stress, we try to do as few transfers as possible. It also seems that some animals have better production if they are able to stay at the original facility they were raised at. However, we must do transfers to benefit the species in the long run. Most BFFs settle down fairly quickly due to all the breeding facilities having a similar setup and routine.

The lighting in the BFF room is a crucial factor for breeding success. The intensity is measured in foot-candles at each enclosure. Day length is also changed according to the time of year. Being from the Great Plains, their lighting needs are similar to our natural light cycle here in Colorado. However, we do adjust it each month going from 8 hours of light from Oct-Dec and increasing one hour each month until May. The increasing day length signals the BFFs to prepare for breeding season.

Male BFFs begin to show breeding readiness slightly earlier than the females. In late December, the testes start to enlarge and sperm production kicks into full gear. They are checked weekly for signs that they are coming into season. This is to ensure that they have sperm ready for when the females come into season later on. As a result of the genetic bottle neck, the sperm quantity and quality is decreased from what normal animals had in the wild prior to the bottleneck. In order to optimize breeding success, we conduct sperm concentration counts to make sure the males are at their prime breeding readiness. The males BFFs are anesthetized for the procedure and semen is collected. The samples that are collected are then loaded into a hemocytometer for counting under the microscope.


a) On each side of the hemocytometer is a square grid that contains 9 squares.


b) Only the 4 outside corners are counted, but on each side of the hemocytometer.


c) There is an even smaller grid within the grid on each side. In each corner, there
are 16 squares.



d) Each square is looked at and the sperm are counted in each of the 64 squares with
the average taken between the two sides. That number is then placed into an
equation to get the total concentration for the volume of semen collected.

Our goal is for the male to have above 250 million sperm per milliliter of semen. If the male is above the goal, then he can be used for breeding. If he is under, then he can be given a few more weeks and tested again. However, if the male is needed for a pairing before he is ready then he will be used if there are no other males available.

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part III: Morning Duties

Black-footed ferrets (BFFs) are extremely susceptible to disease, so their home in Cheyenne Mountain Zoo’s Conservation Center is under strict quarantine. It takes a lot of work to keep up. For example, zookeepers shower before dressing in special clothes and shoes, which are worn only when caring for the ferrets. Latex gloves and face masks are also worn since BFFs, like the domestic ferret, can catch the human flu. These measures are important in preventing catastrophic events such as the plague and distemper outbreak that caused their original brush with extinction.

BFFs are solitary animals. Inside the Conservation Center, each BFF has their own upper enclosure with a tube leading down to a nest box, or burrow. The tube mimics a prairie dog tunnel. Mornings consist of cleaning and checking the health of each BFF. First, each BFF is moved from its upper enclosure to its lower nest box, and the upper enclosure is wiped down with a disinfectant. Next, the BFF is shifted out of their lower nest box to clean and disinfect the latrine side. Cleanliness is key for the BFFs, so each enclosure has its own cleaning supplies and nothing is ever used twice. After disinfecting the enclosure, clean Alpha-dri bedding is put down, which is a special compressed, highly-absorbent shredded paper. Multiply this process by 25 ferrets and you have a busy morning!

After about two hours, the BFFs are all back to sleep in their freshly cleaned nest boxes. We try to limit our time in the room as they are nocturnal, but go back in near the end of the day to feed and check on them. The BFFs get ground meat especially prepared for small zoo carnivores, and twice a week, a rodent. The bones from the rodents help keep their teeth clean and healthy. Since we are part of a reintroduction program, it is very important for their teeth to be in good health for hunting in the wild.



This breeding season (2011), we have nine males and 11 females. In addition, we care for five older BFFs unable to be released. They will eventually travel to other zoos or education facilities.

Celebrating the 30th Anniversary of the Black-Footed Ferret’s Rediscovery - Part II: History

Zookeepers watch cameras through this window in Cheyenne Mountain Zoo's Conservation Center to monitor breeding and births.

The only ferret native to North America, the black-footed ferret once thrived across grass prairies from Canada to Mexico. Today, it’s one of the most endangered mammals in North America.

Our story begins with prairie dogs, the primary food source of ferrets. During the early 1900s, much of North American prairies were converted into farmland. Because prairie dogs were considered pests, they were poisoned. Around the same time, the accidental introduction of the bacterium that causes sylvatic plague, along with the loss of prairie dog habitat, led to the black-footed ferret’s drastic decline. The last black-footed ferret in Colorado was seen near Buena Vista in 1943, and by the 1950s, it was believed very few remained in the U.S. In the mid-1970s, biologists thought they were extinct.

On September 26, 1981, in Meeteetse, Wyoming, a rancher and his dog came across a wild ferret. This led biologists to the discovery of a new black-footed ferret population. Since the species is nocturnal and fossorial (meaning they live underground), very little was known about their natural history. Over the next four years, biologists gathered new information on the life and behavior of this elusive species. Unfortunately, in 1985, outbreaks of both sylvatic plague and canine distemper killed nearly the entire Meeteetse population. After six trapped black-footed ferrets died of canine distemper, the decision was made to bring additional animals into captivity. To safeguard the species, a total of 18 black-footed ferrets were trapped between 1985 and 1987. In 1986, the U.S. Fish and Wildlife Service (USFWS), Wyoming Game and Fish, and the Association of Zoos and Aquariums initiated a captive breeding program for the black-footed ferrets.

Cheyenne Mountain Zoo is one of only five zoos in the world breeding black-footed ferrets. Since 1990, we’ve produced 379 kits, and sent 187 black-footed ferrets to the USFWS’s National Black-Footed Ferret Breeding and Conservation Center in northern Colorado for preconditioning and release into the wild. Other participating zoos include Louisville Zoo in Kentucky, National Zoo’s Smithsonian Conservation Biology Institute in Virginia, Phoenix Zoo in Arizona, and Toronto Zoo in Canada.

We’re expecting this year’s first litter of Cheyenne Mountain Zoo kits soon. Be sure to check back for updates!

Because black-footed ferrets are susceptible to common diseases and don't tolerate noise very well, Cheyenne Mountain Zoo's Conservation Center is closed to the public.

Celebrating the 30th Anniversary of the Black-Footed Ferret Rediscovery

High up on the mountain between the exhibits of the Cheyenne Mountain Zoo and the Will Roger’s Shrine of the Sun, lies a quiet building that very few have a chance to see. This building is closed to guests for several reasons, the main one being that the animals inside are very prone to stress. This means that they do not tolerate noise well and are sensitive to many common diseases. They are also possible candidates for release to the wild and need maintain a healthy fear of humans. The residents inside are endangered black-footed ferrets (Mustela nigripes) or BFFs for short. They were thought to have been extinct twice in their natural history and if it wasn’t for a rancher in Meeteetse, Wyoming and his dog named Shep, they might actually be extinct today.

2011 is a very exciting year as it marks the 30th anniversary of the rediscovery of one of the last wild black footed-ferret populations. The official date of rediscovery was September 26th, 1981. The Cheyenne Mountain Zoo has been involved with the recovery of this species since 1990. As part of the 30th anniversary celebration, we are going to make frequent BFF postings on our blog. Readers can follow along as we gear up for the beginning of the breeding season and see what exactly goes on in an intensive endangered species breeding and reintroduction program.

First, let’s start with some background information. The black-footed ferrets are nocturnal predators that live a solitary life as an adult. They are the only ferret native to the Americas and once lived throughout the Great Plains from Saskatchewan, Canada to Northern Mexico. They are a member of the Mustelidae family which includes otters, badgers, mink and weasels. The BFF is a specialist; it relies almost entirely on prairie dogs for food as well as their burrows for shelter. From nose to tail tip they are 18-24 inches long and can weigh up to two-and-a-half pounds. Natural predators of the BFF are owls, hawks, eagles, coyotes, and badgers.

Learn more about the black-footed ferret and Cheyenne Mountain Zoo's conservation efforts on our website.