At each site, they found the tracks of a fisher, a member of the weasel family and close relative of the marten. Fishers eat snowshoe hares, along with a variety of other small mammals, birds and even martens. They're also infamous as one of the few animals that can successfully attack a porcupine. Their ingenious method is to attack from above while a porcupine is climbing a tree, biting its vulnerable face, according to the Encarta Encyclopedia. Then the fisher turns the stunned porcupine over and attacks its unprotected belly.
Fishers also cache their prey, coming back to eat it later.
McLaughlin found another clue pointing to the fisher when he took the skulls of various predators and compared their teeth with the bite on the kitten's neck. But though the fisher is a formidable predator, it initially was not considered one that might compete with lynx. As part of the study, the team has been monitoring radio collars on six coyotes, four foxes and one bobcat since the study began. Arguing against the fisher as the culprit is its size. Fishers generally would be smaller than a lynx.