WDFW biologists Sara Hansen, center, and Scott Fitkin, right, consulted with a member of the helicopter crew about their mission to collar 36 mule deer does in the Methow Valley.
WDFW study uses helicopters to tag mule deer
EDITOR’S NOTE: This article has been updated to correct the estimated size of the mule deer subherds. (Jan. 30, 2020)
It takes just six to eight minutes to ensnare a mule deer doe in a net, take her body measurements and a blood sample, and fit her with a GPS collar and an ear tag. Ideally, it goes by fast enough that the deer don’t know what hit them.
“It’s kind of like a giant jigsaw puzzle of deer, net, shrubs and person, but it always works out,” said Sara Hansen, statewide deer specialist for the Washington Department of Fish and Wildlife (WDFW). “It’s more controlled than it looks.”
Crews with WDFW collared 36 does this month, reaching their quota for a long-range study of mule deer habitat and migration.
Hansen and a helicopter crew — a pilot, a gunner (who fires the nets), and two muggers (who take measurements and collar the deer) — were in the valley for four days in early January to get a substantial representation of deer from Winthrop to Pateros for the study.
The helicopter skims the open hillsides for deer and, when it finds its quarry, hovers 10 to 15 feet above ground while the gunner fires a net. Weighted corners help the 12-by-12-foot nets wrap around the deer, entangling the animal.
The copter lands and the mugger hops out, gently extricating the doe’s legs and securing front to back legs on each side with a hobble so the deer can’t hurt herself or the mugger. The mugger also places an eye mask on the deer. The deer generally settle down once the hobbles are on, Hansen said.
While the process sounds complex, using helicopters is the most efficient way of collaring deer, particularly on the Cascade slopes, Hansen said. It also tends to be least disruptive to the animals. Once a deer eludes the copter for two minutes, they abandon the chase, she said.
Because collaring the deer is most important, the crew will skip the other procedures if necessary. Blood samples are tested for pregnancy and saved for potential genetic research.
WDFW is using collars that weigh 1.4 pounds, 1% of the average doe’s body weight. Studies have found collars at that weight are the least bothersome to the animals and don’t adversely affect survival, Hansen said.
Helicopter crews carry six nets at a time and then land to pick up nets Hansen and her ground crew have refurbished by removing stray branches and shrubbery.
Lower valley focus
It took the heli crew longer to catch 36 does than expected, since, with little snow cover, many deer remained higher up among the trees. During their first flight, the crew spotted 26 deer in the timber, but collared only two in the shrub-steppe. They have permission to catch deer on both public and private land.
These 36 does replace collared deer that have died in the past year or two, bringing the total collared population from the Methow back up to 99, Hansen said.
The collars are programmed to text and email the researchers if there’s no movement for nine hours, so that biologists can locate the deer and do a mortality investigation. Adult does can live into their teens and have an average 85% annual survival rate, Hansen said.
This month, WDFW focused particularly on the lower Methow Valley, where they believe mule deer use different routes and are underrepresented in their data, Hansen said. WDFW started collaring deer for this research project two years ago, the first time they’ve collared mule deer in the state in two decades, she said.
The WDFW research has three main facets — a study of mule deer migration routes and habitat in the Methow Valley; development of a new method for estimating deer populations; and gathering data for a University of Washington predator/prey study of cougars, wolves and deer. Research results won’t be available for at least another year, since biologists need at least three years of data, Hansen said.
About the habitat
Biologists estimate the combined Methow and Okanogan mule deer subherds at 20,000. The most recent estimtate, in 2017, for the Methow subherd was 15,000, but WDFW biologists believe the numbers have decreased because of the effect of wildfires on their winter habitat.
The best way to increase the mule deer population is through habitat improvements, Hansen said. Other WDFW teams are removing barbed-wire fencing to reconnect deer populations, which benefits animals such as grouse as well. “It’s a big push to prioritize conservation,” she said.
Wildfire is usually beneficial to deer habitat, because it spurs growth of the shrubs the deer browse. But the magnitude and intensity of the 2014 and 2015 fires destroyed a lot of the deer’s winter range all at once, Hansen said. Fawns suffered the biggest impact, since adults outcompeted them for food, she said.
The Methow herd strays as far as the Okanogan and Sinlahekin during the summer. Researchers want to know if the animals follow different migration routes in the winter. “That’s why these collars are so fantastic — we get a GPS reading every four hours,” Hansen said.
Hansen pointed to a map on her laptop of meandering routes taken by individual collared deer. Some deer collared by WDFW cover 40 to 50 air miles and have been tracked into Canada, WDFW District Wildlife Biologist Scott Fitkin said. “The cool part about the deer and how they use the landscape is the migratory stuff,” he said.
Mule deer winter range tends to be more limited, generally within a square mile, although some deer have a winter home range two or three times that size, Fitkin said.
This year, the mule deer in the Methow are in good shape. “There’s more fight in them than in other places,” Hansen said. “They’re strong and healthy — very robust.”
The crew is also capturing and collaring 50 mule deer for new studies in Chelan County and 50 in Kittitas County. Those studies will look solely at habitat use.
Mule deer or white-tail?
Washington Department of Fish and Wildlife (WDFW) researchers measure the metatarsal gland on the back of the lower part of a deer’s rear legs, which provides a definitive distinction between mule deer and white-tailed deer.
As WDFW’s state deer specialist, Sara Hansen often gets questions from people who think they’ve seen hybrid mule/white-tailed deer. Although the two species can interbreed, it’s rare, since their breeding seasons aren’t the same, Hansen said. Moreover, while their territory overlaps, the two species are distributed very differently across the landscape. Hybrids are less likely to succeed in reproduction, she said.
But there are enough variations among individuals in the two species that they can be hard to tell apart, said Hansen, who’s classified thousands of deer. There’s a huge range in antlers — mule deer antlers are generally branched, but some have just a single tine.
The surefire way to distinguish between the species is the metatarsal gland. On white-tails, the gland is the size of a quarter or a half-dollar and has a tuft of white fur. On mule deer, the gland is 6 to 8 inches long with no white fur — instead, it appears as a long, dark slash of brown fur on the back of the leg. In mule deer/white-tail hybrids, the gland looks like a combination of the two.
On white-tail deer (left), the metatarsal gland is very short (~1 inch) and looks almost roundish because it is surrounded by white, often very fluffy, fur. On mule deer, the gland is long (~4-6 inches) and looks very different from a white-tailed deer. Fur around the gland is the same color as the rest of the leg and it can look like a small dark wave of fur running down the back edge of the lower rear leg or it can also just look like a dark line of fur down the leg.
