Longtime DNR pathologist finds the answers in wildlife deaths

During a bald eagle necropsy, DNR wildlife pathologist Tom Cooley does a check of the carcass.

May 22, 2014

If the Department of Natural Resources were in the television business, it would have one sure-fire, prime-time drama on its hands: "Cooley, M.E."

Tom Cooley is the DNR's pathologist. When wildlife - both game and nongame - are found dead from unapparent causes, it is Cooley's job to figure out what happened.

"We get specimens from the public, our own agency personnel, the (U.S.) Fish and Wildlife Service and USDA Wildlife Services," Cooley said.

The DNR's pathologist for 35 years, Cooley spends several days a week in the necropsy room at the DNR's Wildlife Disease Lab (located at the Michigan State University Diagnostic Center for Population and Animal Health), working on everything from skunks to eagles, looking for what killed them.

Sometimes the job is fairly easy; an animal, found by the side of the road with broken limbs and contusions, was likely hit by a vehicle, he said. Sometimes, the cause of death is much more difficult to determine.

DNR Wildlife Disease Lab technician Julie Melotti X-rays a bald eagle carcass.Take eagles, for instance. Last year, Cooley examined 79 eagles. The leading cause of eagle mortality, nearly 50 percent, he said, is trauma and almost two-thirds of trauma death is caused by vehicle encounters. Cooley begins his examination by checking the wings and legs for broken bones and looks for any burned or broken feathers that might indicate the bird flew into an object or power line.

But he finds other causes for eagle mortality, as well.

"Someone brought in a pair of eagles that had locked talons and were found together," Cooley said. "They died from trauma and drowning."

Some 10 percent to 15 percent of eagle mortality is caused by lead poisoning, Cooley said. He and lab technician Julie Melotti fluoroscope every eagle that comes in to check for lead that had been ingested (or inflicted). "We do that for loons and trumpeter swans, too," he said.

Cooley said he's seeing more lead exposure than in years past, something he attributes to the birds scavenging, "most likely either feeding on deer gut piles or on carcasses that were not recovered."

Cooley examined one bird that was banded and more than 30 years old that apparently died of old age.

"When you're dealing with that old of a bird, organ systems may just be wearing out," he said. "And because eagles live a long time, you could be dealing with the effects of pesticides that aren't even used anymore. We always check the livers for heavy metals - specifically, mercury and lead."

This year, there were a lot of waterfowl brought into the lab that were overwintering on the Great Lakes or lakes at power plants, "a lot of ducks , grebes, mergansers and loons were landing on roads or parking lots," Cooley said. "Some died on impact and some starved when they couldn't take flight."

Dead waterfowl were common across the Midwest this winter, Cooley said

"All the states that touch the Great Lakes had waterfowl mortality this year as a result of the lakes icing over," he said.

Cooley always begins his investigation with a gross examination, looking for signs of trauma or other observable symptoms.

"You work from the outside in," he explained. "You look for external parasites - ticks on deer, elk or moose, feather lice on birds - and then you examine them internally for other parasites, such as brain worm in deer, elk and moose. We had heartworm in a wolf this winter; that was a surprise - we don't normally see that.

"Basically, you take your checklist, figure out what it could be, and then start eliminating possible causes of death."

If nothing is grossly apparent, Cooley said the lab will run tests for bacteria, viruses and toxins.

"We've had some deer the last couple of years that when you're finished, everything is negative," he said. "Normally, if you're dealing with a die-off, it's something you've seen before. But there are always emerging diseases; when we first found tuberculosis, none of us had ever seen it before - just pictures in books."

Cooley said Michigan is ahead of the pack when it comes to wildlife pathology.

"There are a lot of states that do not have these labs - they contract out with universities or other states," he said. "We've had this lab since 1933 and we have one of the bigger labs in the country. Michigan has always placed a lot of emphasis on wildlife disease. It's nice to have answers faster as to what caused death; if it's a disease you can do something about, you can react quickly."

Cooley said he saw a fair amount of starvation among deer fawns this past winter, statewide.

"There was no fat on them, the bone-marrow fat was exhausted," he said. "Everything else - they had negative TB and CWD tests - looked normal."

Despite holding down the same job for more than three decades, Cooley - who has a B.S. from Michigan State and a master's degree from Colorado State - said he's never wanted to do anything else.

"I love it," he said. "You never know what you're going to see. There's a lot of variety in what we do and things can change really fast."

Although he's getting a little gray in the beard, Cooley has no immediate plans for retirement - he likes his job too much, he said

"It's fun."

Learn more about the DNR's efforts to understand and manage wildlife diseases - and more about the lab - at www.michigan.gov/wildlifedisease.