Disease Likely Increases Winter Mortality of Black-Tail Deer On North Olympic Peninsula

NEAH BAY(April 17,2008)–A disease called hair loss syndrome (HLS) is one of the culprits in the decline of black-tail deer populations on the North Olympic Peninsula.

That’s the early conclusion of an ongoing black-tail deer study begun two years ago by the Makah Tribe. Alarmed by the fact that Indian and non-Indian harvest of black-tail deer on the North Olympic Peninsula dropped significantly between 1992 and 2003, the Makah tribal council listed the black-tail deer as a species of concern. Black-tail deer are important to Makah ceremonial and subsistence needs.

HLS is caused by non-native species of lice that causes the animal to lose hair from incessant licking and scratching. Infected deer eventually become thin, lethargic and have diarrhea, which can lead to death. Effects are most pronounced during the winter.

“Beyond studying the effects of HLS on deer populations, we also wanted to gather information about black-tail fawn survival rates and mortality sources, because there isn’t much available,” said Rob McCoy, Makah wildlife division manager.

Beginning in 2006, 100 fawns were captured and fitted with radio collars over two years on timberlands owned by the Makah Tribe and adjacent private timberlands. Loose stitching of the collars allows for growth of the fawns and quick release if it becomes hung up on brush. The health of the fawns was assessed from blood samples and body measurements. Biologists and technicians used gloves to minimize transferring human scent and each fawn was returned to the spot where it was found.

Makah personnel have closely tracked the fawns since capture. When radio signals are emitted at a higher rate, it means the fawn died and the tribal staff moved quickly to locate it and determine the cause of death. The results of the study indicate that fawns are particularly vulnerable during the first four weeks of life and then again during the winter. Predation from mountain lions and bobcats were the leading causes of death.

“One of the surprises of the study was the fact that of those fawns that died during the winter in 2006, none died as a direct result from HLS even though more than half of them had it,” said McCoy. Predators accounted for most of the 43 percent winter mortality rate. Of those with HLS, only half survived the winter, while those without HLS had a 64 percent winter survival rate.

“The body condition of all the dead fawns was poor, but those with HLS were particularly bad,” said McCoy. “Although fawns didn’t die directly from HLS, those who have it appear to be more susceptible to predation.” Results from fawns radio-collared in 2007 will not be available until later this spring, but a similar trend is evident so far this winter, said McCoy.

One possible theory for higher mortality rates among fawns afflicted with HLS may be increased vulnerability to predation. “It’s hard for a deer to detect threats when it’s obsessed with itching and licking,” said McCoy. Graduate student Shannon Murphie is currently addressing this theory by monitoring the behavior of radio-collared fawns with and without HLS during the winter.

Estimates of deer populations are used to establish state and tribal harvest levels, particularly for female deer. These estimates use the number of fawns observed during surveys prior to the fall hunting seasons and assumes fawn survival is stable over the winter. “We found higher winter mortality rates than expected and that means we may have been overestimating deer populations.”

McCoy said the study underlines the need for the co-managers to continue to protect female deer from harvest. “There aren’t that many does harvested out here anyway, but if you have a population in apparent decline, you have to protect the females.”
While fawn predation by cougars was high, McCoy said previous studies have shown that cougar control measures don’t usually work unless there is a sustained effort over a long time to suppress predator numbers. “Younger cougars from other areas can quickly replace harvested adults.”

The tribe will continue the study this year. The Makah tribal council provided radio collars and staff time, a federal Bureau of Indian Affairs grant provided for the additional wildlife technician time and supplies, and a State Aquatic Lands Enhancement Account grant will provide for volunteer assistance with capture.

“We couldn’t do this work without the help of the volunteers, our regional co-managers, and local landowners,” said McCoy. KBH Archers, a Bremerton-based sportsmen group, the Quinault Tribe, and the Washington Department of Fish and Wildlife assisted with the fawn captures. Green Crow, GMO, Merrill and Ring, EcoTrust, and the Makah Forestry Enterprise have all provided access to their property.

For more information, contact: Rob McCoy, wildlife biologist, Makah Tribe, (360) 645-3058; Debbie Preston, coastal information officer; Northwest Indian Fisheries Commisson, (360) 374-5501, [email protected]