Biologists evaluating wildlife from the sky

There is a lot of country stretching across the Roan Plateau and the Piceance Basin and wildlife biologists spend countless hours each year flying over this land conducting aerial surveys for deer and elk. Piceance Creek runs lower right to upper left in the photo.

Now you see me, now you don’t. Mule deer dressed in their natural camouflage can disappear against most backgrounds, making it difficult for biologists when doing aerial herd counts. Bucks start to drop their antlers in mid-January.

Less than a month after the end of the regular big-game hunting season, biologists from Colorado Parks and Wildlife are up in the air.

They aren’t being indecisive; instead, they are taking to helicopters to count elk, deer and antelope herds.

It’s a yearly task and these aerial wildlife censuses are key to herd management, including the allocation of licenses and noting how drought, development and other factors have affected animal movement and distribution.

Getting an eyeful from the air also gives a wide-ranging view of key winter and transition range.

“It all looks different from the air, it seems like the world is spread out below,” said Brad Petch, senior terrestrial wildlife biologist for Colorado Parks and Wildlife’s Northwest Region. “But it’s still a challenge.”

The challenge, of course, is picking out a deer or elk naturally camouflaged to blend into its background.

The task is never easy but it’s alleviated a bit if there is enough snow on the ground to offer some contrast.

“Your vision is better if you have solid snow cover and they are out on the snow,” Petch said. “That way, they stand out more, plus you can pick up movement with your peripheral vision.”

But it still isn’t easy, given the various factors involved.

The story still is told of a study done a couple of decades ago by the then-Division of Wildlife in the Little Hills area of the Piceance Basin.

Ground crews had gone out to count every deer in a well-marked area and then biologists were sent up to count the same animals from the air.

“It was tough,” said retired DOW biologist John Ellenberger. “We flew and flew that area and never once got the right number.”

He was speaking during a recent fly-over of the Piceance Basin, where at the time there was about 40-percent snow cover and Ellenberger was pointing out how hard it was to see deer or elk from the air.

“As you can see, once the animals get off the snow and into the brush, it’s much harder to pick them out,” Ellenberger said as we crossed over the Oil Spring Mountain area. “Obviously, we’re much higher now than we would fly during the counts, but you get a feeling for the difficulty.”

Aerial count techniques were being tried in Colorado as early as 1953 but it wasn’t until 1967 that a method was developed to estimate deer numbers across entire herds.

Flights are done to count animal numbers and to figure sex and age ratios, both key factors in setting hunting season.

Because of the size of the region, biologists sub-divide it into mile-square quadrats representative of the various terrain and habitat types.

Counting the animals in pre-selected quadrats and extrapolating that to the entire region gives an overview of how well the herds are doing.

Timing is key to success. You want to wait until there is enough snow on the ground, but you don’t want to wait so long that the bucks start dropping their antlers.

“The big trick is when bucks start losing antlers and then there’s no way to differentiate bucks and does,” Petch said. 

He said deer start dropping their antlers as early as mid-January and the agency usually uses that date as the cutoff for deer flights.

“We hope all the deer flying is done by the middle of January, which means in most years we start around the first of December,” he said.

Elk don’t begin antler drop until later in the winter, so elk census flights are done later.


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