Let me supply the background: The idea was to set up field cameras in front of den sites and observe timber rattlesnakes while they were returning back to their dens. We would also record environmental temperatures outside of den sites via iButtons. Once again, I would team up with fellow colleague Tom Radzio, and for this project we would also get some amazing help from undergraduate Tommy Cerri. We would correlate timing of rattlesnake ingress and environmental temperatures. But there is evidence that rattlesnakes don’t just dive into the den and say goodnight; they hang out in front of the den for a few days and mingle with one another, hear stories about each other’s summer vacations, and bask in the few remaining days above 10 °C. The cameras would capture these behaviors in relation to environmental temperatures. The cameras don’t have audio capabilities, so we are not able to capture the stories of summer vacation, but you’ll just have to take my word on this fact (#nottrue). While relaxing in front of the den and basking in the fall sunlight, the snakes may expose themselves to potential predators. A colleague, Chris Camacho, captured some fantastic pictures last fall showing that predators do in fact visit these den areas (check out more of Chris' fantastic photos).
Okay, so bears are jerks. But we did see something interesting here. We placed the cameras out by the dens well before rattlesnakes began ingress. For one and a half weeks we didn’t see any rattlesnakes or bears. Then rattlesnakes began to come back to the dens, and it wasn’t until this time that we began to see bears visiting these same areas. So there does appear to be a correlation between rattlesnake timing of ingress and bear activity outside of dens. But are we seeing other potential predators? Well we don’t know yet. We have been too preoccupied cursing bears to review all of the videos. The bears did not mess with the tree cameras and perhaps we will see other potential predators visiting the den sites. We are excited to finish analyzing these video data and update everyone on what we find (look for Tommy Cerri’s blog post in the future).
There is another interesting bit of information to digest as well: Bears have never been documented as a predator of rattlesnakes. But we have seen bears swiftly attacking rattlesnake models in the field (see previous blog post). We have also seen bears visiting other gestation sites and den sites. Would it really be too far-stretched of an idea for bears to attack and eat a rattlesnake? But there is the possibility that bears just like to mess with novel things that they find in the woods. There is also the possibility that whatever environmental cue drives rattlesnakes to return to their dens for the winter, also instigates bears to begin foraging for food (other than rattlesnakes) along the hillsides of Pennsylvania. Regardless, bears are jerks.