Within ten weeks the kits stop suckling and begin to walk and climb on their own. At about four months, they can kill their own prey but will remain with their mothers well into their first winter. By the time they are a year old, most have established their own territories. Fishers are solitary animals and are active primarily at night, although they have occasionally been seen at sunrise and sunset, traveling on trails or fallen logs, or moving from tree branch to branch. Occupying the top link of their food chain, adult fishers have little to fear.
Humans are their only major predator.
Eagles, hawks, foxes, bobcats, and black bears, however, all sometimes hunt young fishers. Fishers will eat any animals they can catch, including squirrels, mice, voles, moles, lizards, birds, and insects. But with their low, agile bodies and arboreal abilities, fishers are perhaps best adapted for hunting porcupines. A fisher usually attacks a porcupine on the ground, circling it and biting at its face until it can inflict a lethal bite-a relentless process that can last half an hour. To wear out a porcupine, a fisher occasionally pursues it up a tree and chases it off the end of a branch.