The Bears of Winter

General aviation tracks black bears in Alaska's wilderness

February 1, 2004

As I complete the low pass, with the Aviat Husky some 50 feet above the spruce tree where the bear's den appears to be, the radio telemetry signal in my headset pulses faster. Over the intercom, Mark Bertram's voice from the backseat announces, "Well, that woke her up." It's time to find a place to land the ski-equipped Husky and snowshoe to this black bear's winter den.

It's year four of a study of black bears on the Yukon Flats of north-central Alaska. Bertram and I are wildlife biologists for the U.S. Fish & Wildlife Service, based in Fairbanks, Alaska.

This study will determine the population dynamics of the black bears living in this large basin that lies along the Arctic Circle north of Fairbanks, much of which is a national wildlife refuge. This population of bears is arguably the northernmost black bear population known. At the beginning of our study, we knew only that there were a lot of black bears on the Yukon Flats. Most of our field crews have bear stories to tell when they return from the field.

Gearing up

Early in the summer of 1994, the Fish & Wildlife Service's Cessna 185, mounted on PK floats, was used to move a capture crew to an unnamed lake 30 miles southwest of Fort Yukon. In that aircraft, literally tons of camp gear, personnel, and equipment were moved into the field to begin the fieldwork for this project. Lest you think these government flying jobs are rosy, it's worth noting that more than a third of the weight I hauled to the bear camp consisted of five-gallon plastic buckets filled with "leftovers" from Fairbanks-area fast-food restaurants, including deep-fat-fryer grease. This blend was well aged, of course, to ensure an adequate "aromatic" attraction. Believe me, after the first time the lid comes off one of those buckets during a descent to land, you will never again fly buckets of anything anywhere without checking the security of each top at least twice.

The study area can be reached from Fairbanks, 85 miles to the south, by a float-equipped 185 in about 50 minutes on a good day, so three trips a day is the norm when we're gearing up. The float pond at Fairbanks International Airport, which is 5,400 feet long, is plenty long for maximum-weight takeoffs in the 185, even on the "warm" days of summer.

The first season

Our capture crew established trap sites, using the bait to draw bears to cubbies, each of which is equipped with a padded snare secured to a tree. The bear reaches into the cubby to get at the bait and is held by the snare. Crews checked their six bait stations every six hours for 13 days that first season, and captured 27 individual black bears.

A trapped black bear is neither ferocious nor intimidating. If approached slowly and quietly, it simply sits and watches. A gentle push of the syringe on the end of an extendable painter's pole injects an immobilizing drug, and once the drug takes effect, the bear is removed from the snare, weighed, measured, and fitted with a collar containing a radio transmitter. This transmitter allows us to follow the bear until it sheds the collar or is killed by another bear. Both are fairly common occurrences, so sample sizes must be large.

After the capture phase is complete for the season, the service's Husky on Baumann floats is used to locate each of the bears weekly. The Husky is fitted with two directional antennas, one on each wing strut, pointed outward. The control stick has a rocker switch on top that selects the radio signal coming from the right antenna, the left, or both simultaneously.

The forest and the trees

These radio telemetry flights represent some of the most demanding flying of my 30-year natural resources career. Black bears are secretive denizens of the dense forest. To see a bear you often must make multiple passes as low as 50 feet above the forest canopy. Over the years, I've developed techniques for looking at things on the ground, one of which is to avoid circling the subject. Instead, a racetrack pattern or figure eight keeps me out of my own wake turbulence, and gives me the opportunity to devote full attention to flying while maneuvering and to look out the window only while the wings are level.

The Husky is a superb platform for this work, with its low stall speed and forgiving flight characteristics. A six-hour endurance and 100-knot cruise speed on floats mean lots of time in the study area. Twenty degrees of flaps seems to work well for the telemetry work, with a target airspeed of 70 miles per hour. A little extra speed at these heights is insurance against becoming one with the forest. The moderate flap setting permits the airplane to maintain survey speed nicely, while moderating sudden decelerations because of gusty turbulence in summer's convective air.

Even multiple passes sometimes fail to provide a sighting of the animal. Once I spent nearly 20 minutes working a bear, whose location I knew precisely from the radio signal, yet was not able to spot the animal visually. Finally, during one pass, I happened to glance up toward the horizon, and there was the bear — perched in the very top of the tall spruce tree that I'd been using as my reference point. It's easy to become so focused on the forest that you miss what's in the trees.

Winter's work

Now it's winter on the Yukon Flats, and winter has a very different meaning here than in most parts of the world. This is Jack London country, where temperatures of minus 50 degrees Fahrenheit are not uncommon and, near the midwinter solstice, the sun never rises. March is our chosen time for den visits, since both day length and temperatures are more moderate. Ski flying in the "flat" light of midwinter can be challenging, if not dangerous. With any overcast and a low sun angle, it is very difficult to see obstacles covered with snow. I once landed very near a 5-foot-tall beaver house without even seeing it on an overcast January day.

Bears spend winter in their dens, curled up snugly in a hole dug under the root ball of a leaning spruce tree, covered by 3 to 4 feet of snow. The dens are quite small, to conserve heat, and the den mouth is typically covered with snow. But unlike "true hibernators," bears are light sleepers, and the sound of a ski-equipped Husky passing overhead is enough to cause them to stir.

The bear's collar is equipped with a motion switch, which slows the pulse rate of the transmitter if the collar doesn't move for several hours. During winter's sleep, the pulse rate slows, conserving battery life. During the active summer months, a collar emitting a slow pulse rate suggests a dropped collar or a dead bear, although in one case we followed such a signal to a bear's location in July. As we flew overhead, the signal abruptly changed. Like us, the bears seem to overdo it during the glorious arctic summers, and a long nap feels pretty good in the summer sun.

Wilderness runways

Now, with the bear's den located, it's time to find a place to land. The criteria are simple: large enough to land safely; large enough to take off safely; and hopefully, not far from our bear. As I circle a small meadow a half- mile from the den site, I begin the process of evaluating this off-airport landing site. The first look is a low pass, at 65 mph and full flaps, to get a close look at the proposed landing site, and to feel out the approach and departure paths. If there's any wind, I've already determined its direction and velocity by flying a wind circle, noting the plane's drift as I complete a circle over a point.

The next pass includes putting the skis in the snow, or "dragging" the landing site, followed by a go-around. This improves my sense of the snow conditions, checks for obstacles, and again checks the approach and departure paths. I'll make multiple passes, depending upon snow depth, to better assess the snow conditions, to test for dreaded overflow (free water standing on top of ice, covered by an insulating layer of snow), and to improve the tracks. The goal is to "build" a runway in the snow, and pack down the snow to ease the departure. Stopping an airplane on skis in deep snow is not a problem. Takeoff, on the other hand, can be challenging. There is tremendous variability in both the consistency and character of snow. The challenge of the ski pilot is to learn to read these conditions through low passes and the feel of the skis in the snow, prior to committing to a landing.

Once I'm convinced that this is a credible landing site, I land, make a quick turn around to get back in the tracks, and taxi back to the beginning of the tracks. Another quick turn positions the airplane for takeoff. As soon as the airplane is parked, the engine is wrapped in its insulated cover to keep it warm while on the ground.

If the snow is deep, we spend 20 minutes on snowshoes packing down a strip ahead of the plane to improve the takeoff track. By the time our work is finished and we return to the airplane, these tracks will have hardened nicely in the minus 20-degree temperature.

Dressed in insulated coveralls, we tighten the straps on the snowshoes and prepare for the long slog to the den site. A backpack containing a scale, data sheets, ropes, a tarp, and our
extendable painter's pole goes on Bertram's back, and I carry a shotgun and the radio receiver with its antenna. Moving through the forest (walk is a poor description, since the brush and trees are so close together as to create havoc for snowshoes) we use the directional antenna to guide us to the den.

After what seems like a never-ending trip through the forest, we reach the den. A breathing hole is sometimes a giveaway, but this den is completely covered. The painter's pole is used vertically to find the mouth of the den.

A folding shovel is used to carefully expose the mouth of the den. Once the den is open, it's covered with a black tarp. The drug vials are carried in an inside pocket, to keep them warm, and now we prepare them for injection. Bertram lies near the mouth of the den, peering inside with the aid of a high-intensity flashlight. First he'll determine which end of the bear he's looking at. A black animal curled up in a dark hole makes it tough to tell which end to poke. He's also listening for cubs, since this is a female. Black bears give birth to their cubs in midwinter in the den. It wouldn't do to inadvertently stick one of the little guys with an adult drug dose.

A rude awakening

Today we're in luck. This 14-year-old female has three tiny cubs with her, and they are not happy about the disturbance to their cozy little world. Few creatures can elicit a "fingernails on the chalkboard" sensation as well as baby bears, and these guys are letting everyone know that they are not happy. Bertram finally locates the sow's front shoulder and injects the drug. The den opening is covered and we wait for the drug to take effect. After 12 minutes, we check the bear for responsiveness. Occasionally, a poor injection site or a total miss will require a second dose of drug to be administered, but today mom is asleep on schedule.

Now comes the tough part: removing this amorphous 180 pounds of bear from her den through the tiny opening. Bertram is the tunnel man, being somewhat younger, orders of magnitude more flexible, and, some would suggest, not quite as bright as others in this party. He slides down the hole, attaches a strap to a front leg, and we haul the bear out of her den. Bertram slides down the hole far enough to grab the cubs, and passes them out to me. I shove them inside the top of my insulated coveralls, and being back in the warm and dark, they immediately quiet down, and start looking for lunch.

In the meantime, the sow's measurements, including her weight, are recorded, and her radio collar is replaced. This takes about 20 minutes, by which time the cubs have discovered the primary fault in their current environment, and start yelling for mom again.

It's time to replace the tarp over the mouth of the den, hoist the sow headfirst onto the tarp, and carefully work her relaxed form back through the den opening. The tarp smoothes the way, keeping debris from her eyes and mouth. Once she's in the den, we pull the tarp out from under her.

With the sow back in bed, the gender and weight of the cubs are recorded, and they are carefully placed back with their mother. They immediately quiet, as they recognize the familiarity of their mother's belly.

We place some branches over the den opening, shovel a few feet of snow over the den, and head for the airplane. The return trip goes quickly, since we're not breaking trail, and soon preparations to depart are under way.

Homeward bound

I remove as much frost from the plastic ski bottoms as I can reach, stow the engine cover, and we're ready to depart. After a short engine warmup, I set full flaps, verify with Bertram that he's ready to go, and apply full power.

Acceleration is slow at first, since the snow is more than 3 feet deep, and even with good tracks ahead, there's a lot of drag. The key in any ski takeoff is to keep the airplane in the tracks at all cost, keep the tail ski up out of the snow, and monitor acceleration. The Husky is one of the best skiplanes around. With its 180-horsepower engine and constant-speed prop, it can pull itself out of situations where lesser airplanes would leave their pilots digging and stomping. And muttering. Muttering can be a common component of ski flying.

Today, the Husky crawls on top, accelerates smoothly, and we slip the surly bonds of snow. The temperature enhances the performance and climb capability of the airplane, and we are soon headed south over the White Mountains for the hourlong trip home.

Carrying on a conversation with my backseater, I realize I'm talking to myself, and a glance over my shoulder verifies that my cohort is sound asleep in the din of the Husky's rear seat. At this point in the day, it's the most comfortable seat there is. I have to stay conscious for a while longer, but the flying is beautiful at 6,500 feet, in air so calm it seems like you could swim in it. At this height, the temperature is a balmy zero degrees, so cabin heat is more than adequate.

Back in her den, sow number 511 stirs as she recovers from the drug, then settles back into her winter's sleep. The three little guys have finished their afternoon meal, and are also settling down for a snooze after the most exciting day of their young lives.

Generally a pretty good day's work for us all.


Michael T. Vivion, AOPA 604565, of Fairbanks, Alaska, owns a Cessna 170B.

Topics Avionics