Low snow frustrates efforts to conduct annual moose surveys in northeast Washington
Sun., Feb. 12, 2023
Although snow dusted the hills, it was not enough. That was Annemarie Prince’s prognosis as she and Benjamin Turnock drove northwest of Colville on Jan. 23.
“I was looking at the tree coverage on the mountain the other day,” she told Turnock, referring to her home ski hill, 49 Degrees North. “We’re still gonna need a lot of snow to fly.”
For the two Washington Department of Fish and Wildlife biologists, this is not the idle talk of skiers and snowboarders.
Whether it snows matters, because without adequate coverage they’re unable to conduct the annual moose survey, which indicates the overall population health and determines how many of the large ungulates will be hunted. For decades Washington, like most states, has surveyed its moose population using helicopters. Moose, however, with their drab foliage-adapted pelts, are nearly impossible to spot from the air without a clean white backdrop.
Since Prince became the district wildlife biologist for northeast Washington in 2013, snow cover has “almost always been an issue,” a fact that may be due to climate change, with regional climate models predicting a reduction in snowpack in coming decades.
While Prince’s experience remains anecdotal, she pointed out that Washington used to conduct aerial surveys nearly every winter.
From 1994 to 2012, aerial surveys were conducted each year, according to a 2012 WDFW status and trends report. Between 2013 and 2015, WDFW conducted numerous flights as part of a larger moose population survey project. Those flights were in conjunction with radio collars and thus were less dependent on snow coverage, although Prince said the snow was good during that time. It was unclear if WDFW flew in 2016/17. There were three days of flights during the 2018/2019 winter, no flights in 2019/20 or 2020/21 and one flight, which didn’t provide enough data to be useful, in 2021/22, according to WDFW data.
Biologists haven’t flown this winter.
These surveys give managers a bull-to-cow and calf-to-cow ratio, which determine how many moose may be hunted each year and gives managers an overall sense of the moose population’s health. Nationwide, moose numbers have declined. While Washington and Idaho seemed to be bucking those trends, more recent research also indicates a regional decline.
“For us to feel confident that the ratio we estimate is close to the true ratio, we need a large sample size,” Prince wrote in an email. “Therefore, we need to see a bunch of moose and in a bunch of areas. It takes about two days of flying with good weather/conditions (typically) to see enough moose to calculate a reliable ratio. And unless a moose is standing with a calf, we have to see the back end of the moose to confirm sex because the bulls don’t have any antlers this time of year.”
Moose were first documented in the 1920s in Washington. According to a recent population survey, there are about 5,000 of them, mostly in northeast Washington.
While there have always been years when it was difficult to survey moose, those difficult years “occurred intermittently as opposed to becoming more the rule than the exception,” retired WDFW biologist Woody Myers said,
In addition to reducing snow coverage, the warmer temperatures make it less likely the moose will be in the open, Prince said.
“We’ve noticed that any temperatures above about 35 degrees makes it less reliable that moose will be in the open where we can see them,” Prince wrote in an email. “Especially on a clear day that would be good for flying. They have big dark bodies that absorb heat and so, even 35 degrees on a sunny day is likely ‘warm’ for a moose.”
Biologists are tinkering with other ways of surveying moose.
Those include camera-trap surveys, which Idaho uses to estimate its wolf population and DNA surveys using scat.
Lack of snow is an issue in Idaho, combined with thick tree coverage in the Panhandle, Idaho Department of Fish and Wildlife spokesman TJ Ross said in an email. Those facts pushed Idaho wildlife managers toward “other methods for estimating game animal abundance – the use of game cameras, for example,” he said.
The efficacy of camera trap surveys is still being debated, Prince said, and DNA testing is “crazy expensive.”
For the moment, aerial surveys remain the best option for Washington biologists. When the snow permits.
“We don’t know what we’re going to do with moose,” Prince said. “We’d like to find another way to survey them.”
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