YAKIMA — Nestled along the edges of the Columbia River on the southern fringes of Benton County are several islands where state wildlife biologists occasionally hike to survey the nests of migratory geese.
The islands also often have small populations of deer, some that swim out only during the fawning season and others that stay to enjoy the safe haven from predators.
About 15 years ago, those biologists doing nest counts found something else instead.
“All the deer were dead on the islands. Every last one of them,” recalled Jeff Bernatowicz, a Yakima-based wildlife biologist with the state Department of Fish and Wildlife. “You couldn’t find a live deer.”
The deaths were eventually attributed to a mutated and particularly virulent form of Adenovirus, a hemorrhagic disease known to cause pneumonia in cattle.
“In the places where you can identify the virus,” Bernatowicz said, “it will take out 50 to 70 percent of your deer almost overnight.”
And the virus wasn’t the only killer out there. It, along with a potentially deadly louse that emerged in the mid-1990s, sent Central Washington’s deer population into a steep decline with no rebound in sight.
Why the population remains low remains a mystery. But since last year, a west side tribe has been working with the financially strapped state Wildlife Department to unravel why deer populations remain low in the Yakima region.
In 1995, deer on the west side of the Cascades began getting hit by an exotic Eurasian louse typically found on European and Asian deer and antelope. The louse creates a severe allergic reaction in deer, which respond by obsessively grooming and picking at their coats, creating large hairless patches. On the east side of the Cascades, a different louse named Bovicola tibialis began killing even more deer.
“I think it had a stronger effect over here because of winter conditions on the west side,” said Scott McCorquodale, Wildlife Department deer and elk specialist. “Not having all your hair (there) is not as big an issue as it is over here, where the winters are much colder.”
Over the next several years, deer harvests in south-central Washington dropped by more than 40 percent. Hunters now see the lowest success rate in the state, 8 percent bagged deer compared with the statewide average of nearly 26 percent.
But with more hunters opting to pursue more fruitful hunting elsewhere, a decade of mild winters and at least two microscopic killers identified, why haven’t the Yakima deer rebounded?
“When you look at deer populations, almost everywhere you have these booms and busts,” Bernatowicz said. “Our deer population has never recovered. Why?
“That’s the million-dollar question.”
The Muckleshoot Indian Tribe, though, may help find an answer.
The tribe’s wildlife committee has initiated a four-year deer study that is both extensive and expensive, with the tribe having already spent $200,000.
Since early 2013, the Muckleshoots, who are based in Auburn, have captured and put radio collars on more than 110 female deer in the L.T. Murray, Wenas and Cleman areas. In addition to improving accuracy in population surveys, the GPS-gleaned collar data will help survey techs beat scavengers to any deer carcasses and better determine the cause of death.
“If annual survival rates are low and indicate trouble ahead,” said Mike Jerry Sr., chairman of the Muckleshoot Wildlife Committee, “we may be able to manipulate factors to improve survival rates.”
Only 16 months along, the study has already produced findings.
For one, low doe pregnancy isn’t the problem; the 2013 pregnancy rate was 94 percent. And early mortality results have weighed heavily toward predators, with cougars (11), humans (4) and coyotes (1) accounting for 16 of the 21 deaths among the first 113 collared deer. Malnutrition and age were factors in three deaths, and two were listed as unknown because the scavengers got to the carcasses first.
It’s too early, though, to pinpoint cougar predation as the dominant factor, cautioned David Vales, wildlife biologist with the Muckleshoot Wildlife Program.
“We still need to do femur marrow fat and age analyses of the cougar-killed animals to determine if they were old or weak and may have died regardless of the cat killing the deer,” Vales said. “While the proximate cause was cougar, the ultimate cause may have been something else.”
The Muckleshoots are sharing all survey findings with the Wildlife Department, consistent with the tribe’s long-standing role as an invaluable co-manager with the state on numerous wildlife issues.
The state doesn’t have the funds for annual deer surveys, so the Muckleshoots have filled in the gaps by doing their own on alternate years.
The tribe closed antlerless hunting south of Interstate 90 after the WDFW’s similar closure in light of the declining deer populations.
Muckleshoot hunters are also required to submit teeth and report antler configuration from harvested animals so biologists can analyze biological relationships of harvested animals.
Even with the survey and other management strategies, though, it still may take generations for this region’s deer populations to rebound.
“I think we’re in a rebuilding phase,” said McCorquodale, the state’s deer and elk specialist. “We’re just not back to what people remember as the good old days, for sure.
“But from my experience, when people remember the good old days, it was really never as good as they remember. No matter what they’re talking about.”