Moose Tracks

Light aircraft help conduct wildlife management studies

August 1, 2002

I bank the Husky once more, changing the angle of my next pass to provide better light on the cow moose below me. Finally, I meet with success: Two newborn calves lie next to the cow moose in the dense brush below. I push the power up on the Husky and climb for altitude to make the radio call to the capture crew.

It's the second season of a moose calf mortality study being conducted by the Yukon Flats National Wildlife Refuge. A biologist and pilot, I am flying the fixed-wing component of the project, an Aviat A-1B Husky, and at the moment my goal is to gain sufficient altitude to communicate with the other half of this aviation team, a helicopter crew currently standing by in Beaver, Alaska.

"Beaver Base, Husky 20HY." The reply comes immediately from biologist Mark Bertram, the crew leader for the study, waiting at the helicopter. I inform him that moose 247 has twin calves and conditions look favorable for a capture attempt, and I read him the geographic coordinates of the moose from the GPS receiver in the Husky's panel. Now I assume a loose orbit 1,500 feet above ground level to keep an eye on the cow and wait for the helicopter to deliver the capture crew.

The Yukon Flats is the third largest unit of the National Wildlife Refuge system, which totals more than 8 million acres. The refuge straddles the Arctic Circle and is bisected by the Yukon River. The Flats is home to one of the sparser moose populations in Alaska, and we are trying to determine the causes and rates of mortality of calves in this population. While we suspect bears are the primary predator of moose calves in this area, our study is designed to document specifics, in both the mortality rates of moose calves and the species of predator involved.

The project began in March 1998. A crew of four biologists, a helicopter pilot, and I flew to the village of Beaver to locate and capture adult female moose. Beaver is an Athabaskan Indian village on the Yukon River, about 90 miles north of Fairbanks. In three days, we captured 30 cows, using the Husky to locate the moose and a Bell 206 B III JetRanger helicopter as a shooting platform for a biologist with a dart gun loaded with an immobilizing drug. These cows, fitted with radio collars, formed the basis of our study.

Now it's late May 1999, and each morning I preflight the Husky and depart from Beaver's 4,000-foot gravel runway to locate each of the 27 surviving radio-collared cow moose. Two of the cows we marked last spring have been killed by grizzly bears; the third was killed by a villager. As I climb for altitude, I use a telemetry receiver to scan the frequencies assigned to our moose. A directional antenna attached to each wing strut connects to a switching relay, then to a switch on the Husky's stick, permitting me to listen to the right-side antenna, the left antenna, or both. As I climb, I stop the scanner on each signal, listening long enough to note whether the transmitter is active. If a collar doesn't move for two hours, the pulse rate increases, giving the first clue that a moose may be dead.

Within 15 minutes, I've monitored the signals of all the moose currently on the air. Two of the calves are transmitting mortality signals. That will be this afternoon's work. For now, I begin checking the cows that have not yet given birth, looking for newborn calves.

To expedite this endeavor, I call up each cow's last location from the GPS database, fly to that location, and then search for the cow, using the radio equipment in the aircraft as a direction finder.

It takes 10 minutes each to verify that the first two cows are still without calves. Moose 247, though, is in very dense brush, and though I occasionally catch glimpses of her, it's difficult to get a good enough view to tell for sure whether she has calves. Sometimes this process of intense low-level maneuvering takes as long as 40 minutes before I have the answer. On rare occasions, I simply give it up and hope that tomorrow the cow will be more visible. But today I get a good look at cow 247 after only 20 minutes of circling.

Yesterday this cow was alone in a clearing, so these calves are newborns. As far as the capture team is concerned, the younger the better, since a four-day-old calf can handily outrun any human in this terrain.

As I orbit in lazy turns at 1,500 feet, I hear Joe Trudeau, our contract helicopter pilot, announce his departure from Beaver on the common traffic advisory frequency. Just a few more minutes to orbit, then it's time to go back to work.

Trudeau calls three miles out with a landing light on, and I spot the JetRanger coming toward me. I stay above 1,500 feet, and Trudeau will remain below 1,000 feet during the capture operation, to ensure separation while we focus our attention on the action below. The surface elevation of most of the Flats is between 300 and 500 feet msl.

As the helicopter approaches, I brief Trudeau on the layout, including the location of the moose and a couple of landing sites that he might use to drop off the capture crew. I vector him just to one side of the cow and tell him to slow down as he approaches. As he passes over the cow, I give him a mark, and he reports the cow in sight. Trudeau moves 500 yards up the gentle slope, takes a quick look at the landing zone (LZ) I proposed, and turns into the wind for a landing. While he accepts my suggestion of a landing zone this time, he often rejects the LZs that I propose because of obstacles I can't see from my higher perch. Sometimes he just finds his own spot, and puts the crew on the ground as expeditiously as possible.

The muggers, as New Zealanders call capture team members in this sort of operation, are Bertram and Jim Akaran, both biologists on the refuge staff. Bertram wears a yellow shirt and Akaran wears an orange vest to enable the pilots to tell who's who when the action gets lively. Both men carry handheld radios that permit them to communicate with the pilots. Sometimes a fast radio call can prevent a whole lot of stomping by an angry moose. Both men also carry shotguns, primarily for protection from bears.

As Bertram and Akaran begin their hike to the capture site, Trudeau flies the helicopter to the west and lands in a meadow, where he awaits my call.

Following my directions from above, the crew walks, wades, and crawls to a spot close to the cow and her calves. This is tough country to get around in, and the cow has moved into an area burned by a large wildfire in 1991. Walking is brutal in these areas.

With the muggers crouched just yards from the moose, I call Trudeau to let him know that it's show time. I push up the power a bit, tighten my turns to be able to keep all the participants in sight constantly, stack on a little more airspeed, and settle in for the capture.

As Trudeau approaches at treetop height I vector him toward the moose so that he will pass over the muggers en route to the cow. It wouldn't do for the helicopter to spook the cow toward the crew. Trudeau spots the cow, and the rodeo begins. Trudeau performs a quick stop maneuver right in the cow's face, in hopes that she will break and run from this apparition, with all its noise and rotor wash. The calves drop to the ground and hide, giving the muggers a chance to nab them while mom is otherwise occupied with the helicopter. Some cows are incredibly loyal to their calves and refuse to move for the helicopter. If this occurs, we'll leave her alone and move on to the next customer.

This time it works like clockwork — the cow bolts immediately. As soon as the cow moves, I tell the muggers to run straight ahead 15 yards. As they approach the calves, I tell them to stop, and they quickly spot the first calf. Bertram grabs this one, and I give Akaran directions to the second calf, which is lying down a few yards away. These little creatures aren't as easy to spot as one might think in this cover. Akaran catches the second calf, and the crew weighs the calves, takes measurements, and fits each with a tiny radio transmitter contained in an expandable collar. All the while, the crew keeps watch over their shoulder, in case the pilots fall down on the job, and the cow comes back unannounced.

I divert my attention to the helicopter now, and watch as Trudeau performs an aerial ballet in his effort to keep the cow at bay. The cow repeatedly attempts to circle around the helicopter to rejoin her calves, but Trudeau is nimble and manages to cut her off each time. It won't be long before she becomes bold enough to get past the helicopter, though. We tell Trudeau that his helicopter is all bark and no bite when it comes to momma moose. Nonetheless, he puts on a display of flying skill and precision that most airshow performers would envy.

Soon the cow moves into a stand of tall spruce. With 60-foot-tall trees for cover, the cow won't be slowed by the rotor wash, and she heads for her calves. Trudeau calls with the news that he's lost control of the cow, and I tell the muggers to wrap it up and run north as fast as they can. They drop the calves and start moving quickly.

Just seconds after the muggers depart, the cow rejoins her newborns and nuzzles them. She's lost interest in the crew now, and starts moving her calves to a safer location. I give the muggers directions to a landing zone, where Trudeau picks them up. Two more calves on the air, and it's time to move to the next cow on my list.

I continue my visits to each radio-collared cow, a daily ritual. One can only imagine what the moose think each morning as I circle overhead, trying once again to get a good look at them and their calves.

Not all capture efforts go as smoothly as the one just completed. A few days ago, I located a cow with a single calf in a meadow. This cow had been staying in dense, tall cover, an impossible capture scenario, and we were beginning to think we wouldn't have an opportunity to attempt a capture. But this day, I found her in an open meadow. Everything went according to plan, until Trudeau brought the helicopter to a hover in the cow's face. She bent down, tucked the calf under her chin, and held her ground. As her ears and mane flopped in the rotor wash, it was obvious that she wasn't going to give up this calf. Trudeau tried everything in his box of tricks short of bumping her with a skid, but she wouldn't budge. We moved on.

Another day, a cow got into tall timber, and out of Trudeau's sight for a moment while the crew was catching her calves. Trudeau called that he was losing her, and almost simultaneously she emerged from the tree line, just 10 feet behind Bertram, who was holding one of her calves. Akaran was still searching for the other calf, which I had lost sight of in the melee. I told them to drop the calf and run. The cow trotted up to her calves and watched the muggers depart. In yet another capture, one of the guys fell as the cow approached, and Trudeau intervened with the helicopter to keep the cow from stomping him. Muggers earn their pay on these projects.

After all the cows are checked for the day, I fly to Beaver for fuel and a short break. Then it's time to investigate the day's mortalities. I locate each mortality site and check for live moose. If a predator has killed one of the calves, mom and the other calf will have left the neighborhood. I also try to see if there is a bear present. If it appears that this really is a mortality I call the crew, who take off their mugger hats and put on their Sherlock Holmes hats. Trudeau flies to the site, lands nearby, and they walk to the kill site. They take photographs, look for remains, and conduct a search for any sign of the responsible predator. These sites often contain hair from the predator, snagged on brush. This hair will be DNA-tested to determine the species. Occasionally there are tracks or scat at the kill site. After a thorough investigation of the area, the crew hikes back to the helicopter to fly to the next kill site.

After almost seven hours' flying the Husky, I land at Beaver, refuel for the next day's flight from the barrels cached at the airport, and secure the airplane for the day. It's a short walk to the village school, where we're based — there are no hotels in Beaver. We sleep in the school library and use the kitchen to prepare meals. I change out of my Nomex flight suit into shorts, and go for a run to get the kinks out. I am usually back in Beaver well before the capture crew, which is still investigating the last kill site.

This process continues daily, with short duty breaks for the pilots. For the busiest portion of the calving period, another fixed-wing aircraft joins us in Beaver. Acquiring a good visual sighting of nearly 30 moose in this country is too much for one airplane and pilot. In 19 days of flying I put 97 hours on the Husky, and fly it to Fairbanks for a quick 100-hour inspection.

By early June, all the cows have given birth, and there is less flying to do on this project. I move the Husky back to Fairbanks, to permit me to work on other projects. The helicopter and crew remain in Beaver for a few more weeks to investigate mortalities.

Now I fly from Fairbanks each morning in the Husky or a float-equipped Cessna 206. As I crest the White Mountains, the southern boundary of the Flats, I monitor the telemetry receiver, listening for mortalities. I'm usually in the Cessna with passengers whom I drop off to work on another study. I then fly to the kill site, verify whether it really is a kill, and call in the helicopter crew. At least I have the luxury of a comfortable bed each night, instead of a cot in the Beaver school library.

As the calves mature, they become more difficult for predators to kill. Investigations of kills become less frequent, and the capture crew moves back to Fairbanks. We release Trudeau and his helicopter to other projects, and thank him for his skilled and safe flying. Now if I detect a kill during my daily rounds, I will pass the word via radio-telephone to Bertram in Fairbanks, who will arrange for a helicopter ride to the kill site, usually the next day.

This project provided a better understanding of the challenges that moose face on the Yukon Flats. This is a dangerous place for a moose, especially a youngster. Only 23 percent of the 62 calves in this study survived to 16 weeks of age. Survival to one year was 20 percent. Ninety-five percent of the documented mortalities were predator kills, about half by grizzly bears and half by black bears. One calf was killed by a wolf, and three calves drowned in lakes whose shorelines were covered with bear tracks. While these numbers aren't dramatically worse than other populations, they highlight one of the most significant factors limiting the growth of this moose population.

In Alaska, light aircraft provide the vital tools necessary to conduct wildlife management studies like this one. Without these resources, our understanding of this country and its animal populations would be much more limited and nowhere near as interesting.


Michael T. Vivion, AOPA 604565, of Fairbanks, Alaska, is a wildlife biologist. He has accumulated more than 9,500 hours in 31 years of flying and owns a Cessna 170B.