One of the main things that drew me to fishers was their reputation as a predator. As I mentioned in my last post, fishers are flexible in what they eat and they are extremely skilled at capturing a wide variety of food types. When a fisher kills a squirrel or a woodrat I find it exciting because I know that fisher has helped itself survive for just a little while longer. Yet, fishers are not the only predator out in the woods, and in fact they themselves become the victims of predation (as many of you know).
Research on fishers throughout the western U.S. (including ours) is demonstrating that predators have a significant impact on fishers. In conjunction with our collaborators (IERC and WIL) we can suggest that as much as 60% of our documented mortalities are caused by predation. Interestingly, most of the mortalities we observe occur during the period when animals are actively seeking mates (March – May) or subsequent to the birth of kits when females are actively lactating (April – August).
It makes sense that animals are susceptible to predation during this period because of the frequency with which they forage as well the energetic demands they may be under. In fact, many studies demonstrate animals foraging in risker ways, or places, under a variety of circumstances (one example).Predators may kill fishers simply to remove potential competition and then simply leave the fisher remains uneaten. Other times they may actually consume the fisher leaving only a few remains.
Females and kits are also vulnerable at the den sites as predators such as bobcat (Lynx rufus) often find and climb the den tree. Thus, females are exposed to danger at the den site and while foraging.
Fishers apparently straddle a very fine line between being the hunter and becoming hunted. At present we are still trying to understand the relationships between fisher biology, habitat, and predators that explain the why fishers are more prone do becoming prey for another animal during different times and places.