BAY CITY, Mich. (AP) — At least three Michigan deer hunters have died of heart attacks during the current 16-day season, including two men who were trying to haul away the heavy animals, authorities said.

“I’ve never seen three people die in 48 hours from heart attacks while deer hunting before,” said Dr. William Morrone, the medical examiner for Bay, Midland, Tuscola, Arenac and Iosco counties.

He said hunters need to better prepare themselves for the rigors of the outdoors.

“Deer season comes and bam: I have a rifle, I have a backpack and I’m trudging through the woods,” Morrone said.

The hunters — men ages 57, 65 and 83 — died in Arenac and Tuscola counties. They're just a fraction of the thousands of people participating in the traditional firearm deer season, which began Nov. 15.

Morrone suggested the Department of Natural Resources should require proof of a physical for hunters.

“Better diets, more activity and everybody should think about a physical before this," he said. “Because deer hunting is a big deal in this state, but it’s also taxing the body.”