WALES – No one knows for sure what creature it was that crept out of the darkness behind Leo Michaud’s home and attacked his 16-year-old Doberman pinscher, ripping her head open.

The Doberman, named Dutchess, had to be put down after the Aug. 12 mauling.

That day, Michaud found a den near Dutchess’ doghouse that he believes was home to her attacker. A few nights later, he caught a glimpse of what he thinks was the attacker itself: a large animal, black, gray and brown with wild eyes and a bushy tail.

“The thing was right in the middle of the yard,” Michaud, 46, said.

The animal glowered for a moment and then ran off, disappearing into the den. Soon after, Michaud began looking at pictures of wild animals fitting that description.

He hit upon a suspect: “It looked like a wolverine,” he said.

Experts, however, say that’s unlikely. Wolverines are known to thrive in Canada, but not Maine. And while they are known to scrap with larger animals, a wolverine going toe-to-toe with a Doberman would be extremely unusual.

“They are obviously very capable fighters,” said Dr. Clinton Long, one of the founders of the Wolverine Foundation in Kuna, Idaho. “But even an adult male, to fight and wound a full-grown Doberman, it’s just not very likely.”

Maj. Thomas Santaguida of the Maine Warden Service is almost certain the animal that killed Dutchess was not a wolverine. His prime suspect is a smaller but even nastier creature common in the Maine woods: the fisher.

Wolverines and fishers have similar heads and body shapes, Santaguida said, and it would be easy for someone with an untrained eye to confuse the two.

But the fisher, the only animal on land that will kill and eat a porcupine, is common in Maine and it is also known to go after cats and dogs.

“They are very aggressive,” Santaguida said. “They are very mean. They will hassle a house pet.” He said they almost never attack a person.

Still, Michaud is nervous. He said something vicious may be living behind his mobile home just off Route 126. He has two teenage children who often roam in the yard. The creature’s den is only 40 yards from to the entrance to Oak Hill High School.

An animal damage control officer unsuccessfully tried to trap the animal. Michaud tried to destroy the den by ramming his car into it, but the den proved to be more sturdy than expected.

Maine Warden Service spokesman Mark Latti said the mystery in Wales remains under investigation. If pressed to guess, he agreed with Santaguida that a fisher is the most likely suspect.

Meanwhile, Michaud said he plans to dismantle the den. He’ll either come face-to-face with the beast that killed his dog or he’ll find the den empty and the mystery will continue.

“It’s a freaky thing,” Michaud said. “It’s very weird. I guess you just never know what you’re going to find in your back yard.”