Biologist discusses peninsula moose populations
Whether the Alaska Department of Fish and Game starts predator control on the lower Kenai Peninsula as an attempt to increase the moose population depends on numerous factors, including:
• Available habitat;
• Moose population and density relative to that habitat;
• Health of cow and moose calves; and
• The overall mortality rate of moose.
“Predator control must be based on sound science, cost effectiveness and be broadly accepted by the public,” Alaska Department of Fish and Game research biologist Thomas McDonough said at a talk, “Moose and Wolf Control on the Kenai,” last Thursday at the Alaska Islands and Ocean Visitor Center.
Saying the final decision was “above my pay grade,” McDonough skirted the issue of if predator control — including aerial hunting of wolves — should happen. Instead, he focused on the biology of moose and talked about recent research in Game Management Unit 15A, the upper peninsula, and 15C, the lower peninsula south of the north shore of Tustumena Lake.
“I’m not going to talk a whole lot about wolves,” he said. “There are still a lot of unknowns.”
This winter, McDonough and Kenai Area Biologist Jeff Selinger plan to put radio collars on wolves and assess the population. McDonough said an estimated 40 to 50 wolves live in 15C.
Last month, the Board of Game at its meeting in Bethel reauthorized predator control for wolves in 15C to include an area north of Kachemak Bay and the Fox River Flats. The board authorized a predator control plan in 2012, but never implemented it. That plan would have expired this summer. The reauthorization keeps the plan in place through the summer of 2022.
“We’re keeping it on the books because it’s a tool we may need down the road,” Board of Game chairman Ted Spraker told the Peninsula Clarion. “It’s not imminent.”
Under Alaska’s Intensive Management law passed in 1994, if populations of large game animals consumed by humans — moose, deer and caribou — fall below certain threshold amounts, intensive management must be considered. That can mean predator control measures like permitting private pilots to hunt wolves from the air or directing Fish and Game staff to shoot wolves from helicopters. For officials to decide if predator control should happen, biologists need to give them thorough information.
In his talk, McDonough gave a quick lecture on what he called “Wildlife Management 101.” In the late 19th century, the Kenai Peninsula became world renowned for its incredible moose thanks to huge wildfires that created prime habitat.
Small alder trees on the upper peninsula provided excellent browse, but as trees grew taller, it became harder for moose to feed. In contrast, the lower peninsula has rolling hills with lots of rivers and streams and more habitat.
Habitat is a major factor in determining the carrying capacity of an area to support a wildlife population. There’s also a relationship between productivity and population that can be shown as a curve. Productivity — how many calves are born in a year — goes up as population increases, but it then falls past a certain point.
Where a population lies relative to productivity and population size can be a challenge, McDonough said.
“That’s the trick,” he said. “It’s difficult through research to know exactly where you are on the curve and know the exact right things to do.”
Scientists estimate population through aerial surveys. That’s going on now, as people might have noticed if they see small aircraft circling over the wild country north of Homer. Scientists don’t count every moose, but count them in random grids. Using various formulas they make estimates based on those counts. McDonough said the moose population for 15C north of Kachemak Bay has remained stable in previous counts at about 3,200 moose. The harvest objective for 15C is about 200-350 moose.
As part of moose research, biologists also look at cow pregnancy rates, calf birth and survival rates and twin rates — called twinning, that is, the percentage of twins born to cows. A healthy moose population will high numbers in all three categories. The pregnancy rate for 15A is 70 percent and for 15C is 80 percent.
In bad years, cows may not give birth at all or only have one calf. Area 15A has a twinning rate of about 20 percent and 15C a rate of about 30 percent. The calf survival rate in 15A is about 13 percent and in 15C is about 30 percent. The low survival rate in 15A indicates a declining population while the higher rate in 15C indicates a stable or slightly increasing population size. Bears are the largest group of predators on the lower peninsula.
Research also looks at body fat of cows and calves, which determines survival over winters. One marker of body fat is the percentage in bone marrow. Scientists took measures of road-kill moose by drilling into leg bones. As an animal burns body fat, marrow is the last part of the body to lose fat.
If marrow has a percentage of less than 20 percent, that’s the point of no return, McDonough said. He found that for calves sampled from February to May, many had less than 20 percent bone marrow fat.
“This was surprising to see how many had inadequate bone marrow at the end of the winter,” he said.
Putting all that information together can suggest how strong a moose population is and how close it is to carrying capacity. In a slide he showed comparing 15A to 15C, the moose population in 15A is near carrying capacity while 15C is below carrying capacity.
“In general, 15C has relatively high densities and relatively good production of young, OK survival, but there’s some measures that indicate initial signs of nutritional constraints,” McDonough said.
That means if the habitat can support more prey animals, predator control can increase the population. If the habitat can’t support more prey animals, predator control won’t work. That’s the situation in 15A, where poor habitat limits moose. Because of poor habitat and a limited area where aerial wolf hunting can be done, biologists will recommend to Fish and Game officials that aerial wolf hunting not continue. Aerial wolf hunting is prohibited in the Kenai National Wildlife Refuge, a large part of 15A. Area 15C has more areas open to aerial wolf hunting on state and, with permission, Alaska Native corporation land.
At last week’s talk, one woman asked if 15C’s moose population was within Intensive Management thresholds, why should predator control be considered?
McDonough again said that was a decision for the commissioner’s office to make. The board of game said they wanted wolf control to happen, he said.
“We’re within thresholds of population size and harvest. My understanding is within their plan they can initiate that control,” he said.
Under the intensive management plan, the harvest is about 200-350 moose. One man at the talk noted a high number of illegally harvested moose last year, about 70, hesaid. Along with legal and illegal hunter kills and predator takes, biologists also have to consider mortality from road kills. The lower peninsula had about 40 road kills from July-December last year. McDonough said some moose struck by cars survive the impact but may wander off into the woods and die.
Along with nutritional data and population estimates, that’s all information scientists present to officials.
“It’s up to us to bring those details to them that would affect moose stability year to year and the challenges of meeting the Intensive Management objective,” McDonough said.
But the public also has a role in helping officials decide if predator control is needed.
“It’s the resource of the public, and the public should weigh in on it, whether it’s great or if it should not happen,” McDonough said.
Michael Armstrong can be reached at firstname.lastname@example.org.