Herd Scratcher—Why Are Some U.S. Moose Dying Off?

The moose population in Colorado is on the rise. Elsewhere? Not so much.

moose population in colorado

A moose shakes water from its face in Grand Teton National Park, Wyoming, on August 7, 2011. (Photo: Lucy Nicholson/Reuters)

has an ASME Award, edits for Backpacker Magazine and writes for Outside, Skiing, and more.

Not long ago, while driving my daughter to daycare, we came upon an open meadow on the road near our house. Near a patch of trees I saw movement. Hollis named it first. “Look, Mama!” she shouted. “A baby goose!” While it was off-the-hook adorable to hear a 22-month-old say goose, she had the object of her amazement wrong.

Out in the meadow, near a pond rippling with tadpoles, were a moose cow and its calf. The cow stared at us, but the calf bounded a few feet from its mother, stopped, looked back, and kept bounding. We were 10 miles from the town of Nederland, where my friends often report seeing the giant willow-eating animals. But while people tend to think that moose have been in Colorado forever, Andy Holland of the Colorado Department of Parks and Wildlife says they’re here because they were transplanted by wildlife managers back in 1978.

They came as a package of 12 that were deposited not far from Rocky Mountain National Park. The moose prospered, spreading across the mountains and into the foothills west of Denver. Today, their numbers top 2,300, thanks to prime habitat and several other additional transplants. Most Colorado moose come from Utah or Wyoming, says Holland.

But wildlife managers in several states are currently puzzled over why moose herds are kicking ungulate butt in Colorado, while herds in Minnesota, Montana, and Wyoming are dwindling dramatically.

Recently, the Denver Post reported that in Minnesota, “state game managers canceled the 2013 moose hunting season because of herd declines of as much as 35 percent. Losses were heaviest in the northlands, where warmer winters have favored blood-sucking ticks that attack moose and leave them more vulnerable to sickness and predators.”

The Denver Post also reported that once robust moose herds in Montana are now mysteriously shrinking, and moose populations in Wyoming are under attack from a brain worm that has reduced their numbers from 2,000 to several hundred. Montana has launched a 10-year study, planning to put radio collars on 90 moose to try and figure out why they’re struggling. And they’re looking at Colorado moose to try and understand why they’re thriving.

One reason, many speculate, is the relative lack of predators in Colorado’s high country. While there are a few documented cases of black bears and mountain lions attacking small moose, in Colorado there are no wolves, which live in each of the three other states.

According to wolf trappers I’ve observed in the field in Alaska, wolves will go on a “killing spree” of moose calves, often “eviscerating” them and leaving them to die while they pursue the next calf. I’ve never heard wildlife managers in the Lower 48 report seeing this kind of activity, but one could surmise that wolves in Alaska probably act like wolves everywhere.

Colorado wildlife managers do say that the moose population in Colorado is now approaching “maximum capacity,” and, says the Denver Post, Colorado Parks and Wildlife is now launching a study to determine how many moose is too many and the extent to which people can coexist with moose as they migrate close to communities. Holland says that the reason moose were introduced to Colorado in the first place was for “hunter and wildlife viewing opportunities.”

Using “hunter dollars,” they’ve continued to “transplant them” to Colorado, and to several other areas in addition to the original. Moose populations have continued to grow in the original area and all new ones, says Holland. And the way the Colorado Division of Parks and Wildlife has controlled numbers—and plans to continue controlling them—is by adjusting the number of moose hunting licenses it issues each year.

“Demand for licenses to hunt bull moose—$251 for residents, $1,951 for out-of-states—is higher than for any other big-game animal in Colorado,” reports the Denver Post. “We’re not talking about huge increases in moose tags,” says Holland, “but 10 more here and 10 more there.”  

This writer can’t help thinking about all the reintroduced Northern Rockies wolves that now roam Idaho, Montana, Wyoming, and parts of Washington and Oregon. The federal government just made plans to remove them from the Endangered Species List, allowing states to decide how to manage them. Management in recent years has included aggressive hunting and trapping seasons designed to drastically reduce wolf populations, reports the Center for Biological Diversity. In the northern Rocky Mountains more than 1,100 wolves have been killed since protections were removed; this year populations declined by seven percent, it says.

Maybe Colorado wildlife managers should consider transplanting wolves here, too, to help keep the exploding moose population in equilibrium.

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