Fishers are the only natural predator of porcupines, and a surge in their population can kill a lot of trees. I suppose it's all part of the "circle of life", I'd just prefer our pets could sit outside that circle.We have a farmer a couple miles from us that got hit by fishers and took out almost 30 birds in one night. The PAGC released them 2 or 3 years ago to take care of some other problem and now they are becoming the problem.