JWM: New moose count doubles eastern Washington estimates

Counting moose (Alces alces) isn’t an easy task. It helps to have a helicopter, but even then, the moose blend in with the ground and disappear under tree canopies. That makes it hard to get good numbers, particularly in eastern Washington. The region’s relatively new moose population tends to vanish beneath the region’s interspersed conifer forests.

Biologists believed moose numbers had been rising — and are now falling — but rising and falling from what? How many of them were there? Managers could only guess.

TWS member Rich Harris, section manager for the Washington Department of Fish and Wildlife, wanted to get a better number. Using a mixture of helicopter spotting and mathematical equations, he came up with a population about twice what biologists had previously believed.

“When I told other folks at a moose conference that I was attempting to get a moose estimate, they kind of looked at me and rolled their eyeballs,” said Harris, a co-author on a paper describing the technique in the Journal of Wildlife Management.

Population counts aren’t needed all the time, Harris said, but having a good set of numbers will help estimate how the population rises and falls over time. That’s particularly important now, he said, as gray wolf (Canis lupus) numbers grow in the state, raising public concerns about how they’re impacting moose. Wolves may be contributing to moose declines, Harris said, but they’re just one of many factors.

“Moose populations often have a boom-and-bust character,” Harris said. This population, which became well documented in the 1970s, has overwhelmed the available habitat, he said.

“Combine that with climate change — which has made a more hospitable climate for ticks — and the expansion of wolves, and you get all kinds of reasons for the moose population to decline,” he said.

Previously, Washington wildlife biologists had a “guesstimate” about how many wolves were in the region, Harris said. His team set out to get more concrete numbers. Using helicopters in the winter, when snow on the ground made the moose easier to spot, they set out in 2014, 2015 and 2016 along 2,241 kilometers of line transects. Using two observers to double-check one another, they paired the observations with data collected from collared animals and created a mathematical model to estimate the population of moose throughout a 10,513-square-kilometer area.

They came up with an estimated 5,169 moose in the region — or some number between 3,510 and 7,034. That’s much more than managers had estimated, but those numbers are likely to decrease, Harris said, as moose outgrow the ecosystem.

“Most moose are in poor body condition,” he said. “We have moose tipping over and dying. That has nothing to do with wolves.”

TWS members can log in to Your Membership to read this paper in the Journal of Wildlife Management. Go to Publications and then Journal of Wildlife Management.

Header Image: ©Sandy Brown Jensen