To catch a ferret
By Bridget Macdonald, U.S Fish and Wildlife Service, North Atlantic-Appalachian Region
Every fall, Nick Kaczor loses sleep over black-footed ferrets. These cute but fierce predators, which prey almost exclusively on prairie dogs, once numbered in the tens of thousands across Colorado’s Western Slope and Eastern Plains. But the loss of prairie dog habitat during the 20th century led to the dramatic decline of the species that eats them. By 1986, only eighteen individual black-footed ferrets were known to exist in the wild.
But that’s not what keeps Kaczor awake at night. He’s part of a team of scientists who start their workday at 9:00 p.m. for 10 nights in September and October during black-footed ferret survey season at Rocky Mountain Arsenal National Wildlife Refuge. They’re up all night because the ferrets there are doing so well.
“We are extremely happy with how successful the population has been here,” said Kaczor, who is the assistant manager of the refuge on the outskirts of Denver.
Today, this urban wildlife refuge is home to one of the largest populations of black-footed ferrets in the world — a population descended from the 18 wild individuals discovered in the 1980s. In 1991, several of those last ferrets became the genesis for a captive-breeding program that has produced 4,500 black-footed ferrets to date.
Hundreds of native ferrets have been released into the wild at 25 relocation sites across the Great Plains that offer the space and resources ferrets need to do their thing: hunting prairie dogs and commandeering prairie-dog burrows in the middle of the night. Cute, fierce, and sneaky.
Back in 2015, 32 ferrets were released at Rocky Mountain Arsenal National Wildlife Refuge, a 15,000-acre oasis for wildlife on the edge of one of the fastest-growing cities in the west. Kaczor estimates that the refuge is now home to a population of 55 ferrets and counting.
The annual ferret survey provides the baseline for this estimate. The data that scientists collect during these all-nighters help them chart the ferrets’ population growth and keep tabs on individuals. During the survey, ferrets are trapped, examined, and vaccinated for canine distemper, sylvatic plague, and rabies. For the ferrets, it’s a lot like having the doctor make an annual house call with preventative medicine to keep them healthy. These endangered mammals are high-priority patients, so staff must stay alert and focused throughout the entire graveyard shift.
As a Public Affairs Specialist in Massachusetts, for whom the stakes for staying focused at work are a little bit lower, I was thrilled to be invited along in early October to see what it takes to keep a nocturnal endangered species on the road to recovery.
Happily, I could not remember the last time I’d pulled an all-nighter before I joined Kaczor for a night of ferret wrangling. So I asked him for advice.
“Try and catch a nap the afternoon before, and have some coffee,” he suggested.
I did follow his instructions, but in the wrong order. Unsurprisingly, after having espresso around 3:00 p.m., I was unable to nap. I still made it through the night, though. Here’s what I remember:
9:00 p.m. — Staff and volunteers gather in the “Operations Center” for the nightly safety briefing and game planning. Kaczor divides the team into four crews, three of which will be responsible for surveying 1,200-acre areas of the refuge, and a fourth that will staff the mobile Black-footed Ferret Lab — a trailer with a tiny operating room where captured ferrets are given microchips, vaccines, and booster shots before they are released back into the wild. The lab also has a space heater, which I would come to appreciate after riding around in a truck with the windows down for hours on end on a cool October night. Brr.
10:00 p.m. — I set out with Kaczor and seasonal biotechnician, Erin Mihlbachler, for our 1,200-acre tract in a pickup truck with spotlights mounted in the driver’s and passenger’s windows. (That’s why the windows are down!) The high-powered beams enabled Kaczor, (driving) and Mihlbachler (riding shotgun) to continually scan the horizon. Yes, we are searching for ferrets with giant flashlights.
Scientists use high-powered spotlights to scan the prairie for black-footed ferrets at night. Credit: Bridget Macdonald/USFWS
“Ferrets have a different lens than we have,” Kaczor explained. Called the “tapetum lucidum”, the intraocular reflective structure is common in many vertebrates, particularly nocturnal animals. It helps them see better at night and it’s also highly reflective. “When our lights hit their eyes, they illuminate an emerald green,” Kaczor said. Spooky! And convenient.
11:30 p.m. — After an hour and a half, we haven’t seen any ferrets, but we spotted bison, jackrabbits, killdeer, ferruginous hawks, a great-horned owl, a skunk, a playful coyote, and more deer than I have the capacity to count two hours past my usual bedtime. “The prairie really comes alive at night,” Kaczor observed.
11:55 p.m. — Breaking into a bag of Goldfish crackers, Kaczor admits to having raided his six-year old’s snack supply. Secretly wish I had some Goldfish. Eat a granola bar instead.
12:30 a.m. — First ferret sighting! At last, Mihlbachler’s spotlight catches two characteristic green orbs glaring back at us from atop a prairie dog burrow. After examining the ferret through binoculars to determine whether or not it has been caught recently (if it had been, we would have seen a black “X” made with hair dye on the ferret’s buff-colored chest), Kaczor drives directly toward the burrow to scare the wiley critter down into the hole.
Then, parked with the headlights shining on the burrow, Kaczor takes a long, narrow, rectangular cage equipped with a trap door and wrapped with heavy, dark cloth from the back of the truck. He sticks the open end of the cage into the hole.
Meanwhile, Mihlbachler blocks off nearby burrow holes that are potential escape routes with Big Gulp cups. “They’re the perfect size,” Kaczor says. “We buy them in bulk from a restaurant supply company.” This tactic prevents the ferret from exiting through a burrow other than the one where the cage has been placed to capture it.
Although the trap seems rather conspicuous to me, Kaczor insists, “Ferrets are super curious — we’ll come back in about an hour and probably find one in there.”
Super curious, or super surly? The answer is both.
1:08 a.m. — Second ferret sighting! Trap set.
1:31 a.m. — Third ferret sighting! Trap set.
1:43 a.m. — Fourth ferret sighting! Trap set.
1:53 a.m. — Fifth ferret sighting! Trap set.
2:05 a.m. — Sixth ferret sighting! Trap set.
2:23 a.m. — Seventh ferret sighting! Trap set.
3:01 a.m. — Ninth ferret sighting! Trap set.
3:02 a.m. — Realize I have lost count of ferret sightings.
3:40 a.m. — We revisit one of the traps we set earlier, and discover a new ferret. We know she’s new because she is hair dye- and microchip-free. When staff catch a new ferret, they implant the animal with a microchip — the same technology veterinarians implant in dogs and cats. “It’s tiny, about the width of a pencil lead,” Kaczor explains. That helps staff keep tabs on that individual and tally the total number of ferrets on the refuge. After thoroughly waving the chip reader with no readings, Kaczor loads the ferret into a transport tube to deliver it to the lab.
4:30 a.m. — Kaczor drops me and the new ferret off at the ferret lab. In the tiny operating room, Amanda Fox guides two new technicians, Monique Rivera and Katie Sellers, through the ferret health check-up procedure. The animal is carefully conveyed from the transport tube into a small chamber where it is exposed to isoflurane, an anesthetic gas, for about three minutes, and then removed gently by Fox, who is wearing welding gloves just in case. Like I said, “Cute but fierce.”
The technicians then place a face mask connected to a hose over the ferret’s snout, providing a continual feed of isoflurane — seriously, an awake ferret is a bitey ferret — while they implant the microchip, administer vaccines, take measurements, apply hair dye, and estimate age based on the color of the teeth. “They are nice and white, so we’ll call her a kit,” Fox says.
They then place the ferret in a cat carrier to recover before she is returned to her burrow.
5:00 a.m. — Back in the field, I am now at the helm of one of the spotlights, which leaves me with great admiration for the staff who work these things for hours, night after night. It is both awkward and surprisingly tiring to rotate the light steadily, with cold hands, while bouncing across the prairie, terrain that is not as flat as it looks. I am astounded that Kaczor can do it while driving — a true professional.
5:05 a.m. — I spot a ferret! Binoculars reveal it has a splotch of fresh black hair dye on its chest, meaning it has been caught recently. Still, I feel this is a defining moment in my career with the U.S. Fish and Wildlife Service. I also feel deliriously sleepy.
5:30 a.m. — Eventually, we make our way back to the hole in the ground where we had trapped the new female to let her go. I am invited to do the honors, and imagine her darting dramatically into her burrow with an indignant squeak as soon as I open the cat carrier door. Instead, she does nothing, apparently not interested in leaving her cozy little recovery room. After some gentle encouragement, she finally slips into the dark burrow, a little groggy, but significantly more resilient to the dangers of disease that threaten her species. Black-footed ferrets are still considered one of the most endangered land mammals on Earth. Diseases like non-native sylvatic plague are a major hurdle to recovery, although scientists are searching for solutions, like deploying tiny peanut-butter flavored vaccine baits to protect prairie dogs (and thus ferrets) from the ravages of plague.
This little ferret, Kaczor explains, represents future generations at Rocky Mountain Arsenal National Wildlife Refuge and, one day, beyond. “The refuge can probably support a population of about 100 black-footed ferrets, so once that goal is achieved, we envision Rocky Mountain Arsenal as a kind of wild nursery that can help provide healthy ferrets to other sites,” he said.
Get it, girl.
6:30 a.m. — Sightings taper off as the ferrets bed down for the day. Crew members, ready to do the same, head back to the operation center to stow equipment and upload data. Although bleary-eyed after a long, chilly night on the prairie, I can clearly see the future is getting brighter for the black-footed ferret. Serendipitously, a pink glow appears on the horizon.
Learn more about black-footed ferrets at Rocky Mountain Arsenal National Wildlife Refuge. Visitors can see these rare mammals up-close at the refuge’s Ferret House and Outdoor Exclosure.
