The Fisher is native to the North East USA and is a member of the weasel family. Fishers are aggressive hunters and prey on squirrels and other small mammals. The fisher is one of the few successful predators of porcupine.
Fishers are very agile and can quickly climb trees after prey, and can reverse their rear claws to enable them to run down the tree as well.
Here is a Youtube video featuring Fishers in the Highpoint Preserve.
The Fall Conservancy newsletter has a great article by Maggie Lin, Program Assistant for NYS Master Naturalist Program.