Idaho biologist develops way to track wolf pup survival rate
Lacy Robinson needed to know how many North Idaho wolf pups survived their first year.
Not an easy task, the state wildlife biologist soon realized. Most wolf pups looked alike in the grainy images captured by infrared trail cameras, making it difficult to identify them in subsequent photos. Aerial counts had limitations, too. By the time the pups were about 6 months old, they were nearly as large as adults.
“It’s easy to count litters of pups in the spring,” Robinson said. But figuring out if those pups were still alive at the end of December was a challenge.
So Robinson, who works for the Idaho Department of Fish and Game, developed her own techniques for tracking survival. The methods have proven so successful that they’ll be deployed statewide this year.
Robinson’s research has her climbing into wolf dens to put custom-made collars with tiny transmitters on blue-eyed pups, and swabbing their scat for DNA. This year, state wildlife officials expect to collar 80 to 90 wolf pups and expand Robinson’s work with DNA identification.
“This is cutting-edge work,” said Jim Hayden, Idaho Fish and Game’s staff biologist for wolves, bears and lions. Nationally, “there aren’t very many pup survival studies.”
Understanding pup survival is critical for the Fish and Game department, which has been managing gray wolves since the northern Rockies population came off the federal endangered species list in 2011.
The state must report Idaho’s wolf totals and number of breeding pairs to the U.S. Fish and Wildlife Service annually, documenting that the state has at least 150 wolves and 15 breeding pairs. Breeding pairs are defined as wolves that produce at least two pups that survive through Dec. 31.
Knowing pup survival rates is also a basic tool of wildlife management, Hayden said. State officials do similar tracking with fawns and other young animals.
Robinson’s early research indicates that wolf pups are vulnerable to hunting and trapping during their first year.
Last year, she collared 15 wolf pups from two North Idaho packs. Six are still alive; seven were killed by hunters and trappers; and two died of natural causes.
Wariness of traps and human scent appear to be skills wolves develop over time, said Robinson, who once came across a grizzled, old wolf digging up a trap in Idaho’s Selway region.
But state officials will have a more complete picture of pup mortality after this year’s collaring effort, Hayden said.
Robinson worked with a Minnesota company to develop collars that would expand as the pups grew and eventually fall off. The collars, made by Advanced Telemetry Systems, weigh less than 3 ounces each, so they don’t hamper the pups.
There’s a 14-day window to get the collaring done, Robinson said. The work has to be done while the pups’ vision is still developing, so they’ll run back to the den for security. If they’re older, they’ll scatter when startled and be nearly impossible to catch, she said.
The DNA testing also holds promise because the biologists don’t have to actually handle the pups, Robinson said. By swabbing scat with a toothpick, she collects cells that yield DNA, allowing individuals to be identified.
Researchers can return to a pack’s territory later in the year to get additional samples, determining which pups are still alive.
Both methods cost less than collaring adult wolves, a time-intensive endeavor that runs about $4,000 to $6,000 per animal, Robinson said.