Biologists Stalk Elusive Solutions Declining Elk Herds In The Clearwater Basin A Complex Problem

When people want to describe a complicated subject they often compare it to rocket science.

Wildlife biology would make a far more accurate analogy, Idaho Department of Fish and Game biologist Steve Nadeau said.

“Rocket science is mathematics and physics,” he said. “Wildlife biology is so much more complex than that.”

Consider the relationship of predators and prey. Next, throw in multiple predators and more than one prey base. Add on top of that a predator that can subsist almost entirely on vegetable matter and another that is elusive and difficult to study.

That is exactly the situation in north-central Idaho, where black bears and mountain lions thrive. Some say the predators are thriving at the expense of the Clearwater Basin’s renowned elk herds.

That might be the case, Nadeau said, but it might not. The biology is too complex to say more predators mean less prey and fewer predators will lead to more elk.

“We don’t think it’s a one-to-one ratio with predators,” he said.

If a hunter kills a bear, that does not necessarily mean an elk will be saved. In fact, Nadeau said, 100 bears could be killed without saving a single elk.

On the other hand, killing one or two bears could save several elk. That’s because not all bears prey on elk calves and some prey on many.

“Elk predation is a learned behavior,” Nadeau said. “Some bears really focus on elk calves and others don’t know what to do with them.”

To find out what the relationship is between predators and the nose dive elk herds have suffered in the region, the department has initiated a bear study and experiment in conjunction with an ongoing elk study.

One of the aims is to see what role predation plays on elk calf survival rates. To do that the department first set out to establish a population estimate of the bears in the study area.

Next they hope to manipulate the bear population to see if it will have an effect on the elk herd. The plan is to reduce the bear and lion population by 50 percent in the study area through increased bag limits.

Beginning this fall, hunters will be allowed to take two bears and two lions in a portion of Unit 12. The length of the season there also will be increased.

Unit 10, where the season and limits will stay the same, will be used as a control. In a portion of Unit 15 along the South Fork of the Clearwater River, where there are fewer bears and lions and elk calf survival is much better, bear and lion hunting will be eliminated.

Biologists will see if an increase in the bear and lion populations will affect the survival rates of elk calves.

“I think in Units 10 and 12, if we achieve the sorts of harvest levels we’re talking about, we’ll see fairly dramatic changes,” Nadeau said. “If we don’t get the harvest it could take a long time.”

Biologists know predation plays a role in elk numbers, but it’s not as easy as some think. Many factors come into play.

Some prey and predator populations rise and fall together. But bears and lions in north Idaho also have a healthy population of deer to prey on when elk numbers head south.

Because of that, the numbers of each can stay high despite a drop in the elk prey base.

“Predator-prey relationships are much more complex than anyone has studied before,” Nadeau said. “In some instances we need to relieve the pressure on prey animals; in other instances it makes no difference.”

Bears and lions are not the only predators in the basin. Coyotes and now wolves also move through the area.

Weather is another factor that complicates the situation. A few harsh winters can cause elk herds to plummet despite good habitat and low numbers of predators. Likewise, mild winters can allow elk populations to grow even with the presence of dense bear and lion populations.

Nadeau said there is no indication the North Fork and Lochsa drainages have any more bears today than they did in the 1970s.

Mild winters then may have allowed elk populations to stay high despite a high number of bears.

“We try to do the best we can when conditions are constantly changing,” he said. “We can’t be knee-jerk reacting to low (calf survival) and say it’s predator-related in every case.”