The Lizard Log

The Langkilde Lab in Action


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Bears Are Jerks (and Other Things I Learned Along the Way)

I would have done it differently.  Yeah, I think that is a good way to start this post.  But everything makes more sense in hindsight.

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).

Red-tailed Hawk landing in front of a den site with a Timber Rattlesnake in front.

Red-tailed Hawk landing in front of a den site with a Timber Rattlesnake in front.

Fisher checking out den site.

Fisher checking out den site.  These are some pretty carnivorous animals!

Raccoon nosing around the entrance to the den.

Raccoon nosing around the entrance to the den.  It appears it is really looking for something.

Momma Black Bear and her cubs walking past a Timber Rattlesnake den.

Momma Black Bear and her cubs walking past a Timber Rattlesnake den.

So this year, we staked out three den sites with field cameras.  We placed two field cameras at each den site.  The one camera was on a tree about 8 meters from the den.  This camera would capture potential predators as they stopped by to visit the den.  The second camera would be much closer to the den and capture the rattlesnakes as they moved in and out of the den.  However, there was a problem with trying to put a camera so close to the den site… the problem was that there wasn’t always a tree right next to the den.  Problem solved!  I built a wooden stand that would support the camera and keep it focused on the den site.  To standardize things, we used this wooden stand for all three den sites, but kept the second camera farther away on a tree (the picture below is taken by the tree camera and you can see the den camera in the background).

Camera positioned directly in front of rattlesnake den.

Camera positioned directly in front of rattlesnake den.

This stand worked great.  And we soon began to capture a few rattlesnakes as they came back to the den site.

Timber Rattlesnake relaxing in front of den.

Timber Rattlesnake relaxing in front of den.

Rattlesnake basking in front of den entrance.

Rattlesnake basking in front of den entrance.

And then we even began to see some bears as they visited the den sites…

Fir

First Black Bear to visit one of the den sites.  This was a nice bear.  Thank you nice bear.

And then the bears became jerks.

Black Bear sitting in front of camera and bending camera over so that it can gnaw on it... jerk.

Black Bear sitting in front of camera and bending camera over so that it can gnaw on it.  The camera was attached to the wooden stand by a thick metal bolt… the bears just bent these bolts like they were flimsy plastic… jerks.

Bears even tag-teamed the camera at times...

Bears even tag-teamed the camera at times!  Not one, but TWO BEARS!!! …double jerks.

Perhaps the bears just like to mess with novel items placed in their habitat.

Bear Hug....

Bear Hug….

Bear chewing on camera...

Bear chewing on camera…

Bear sitting down and swatting the camera round and round.... jerk.

Bear sitting down and swatting the camera round and round.  REALLY! This bear just sat there for 10 minutes swatting the camera as it swiveled around and around on the bolt…. jerk.

Perhaps the camera and stand actually look like some weird creature that lost its way in the woods.

Maybe this is what the bears see?

Maybe this is what the bears see?

Regardless… we stopped seeing rattlesnakes enter the den….

Our

Our “Den Site” View for the majority of time…. Maybe the snakes will go up in the trees…

We did get some great pictures of the backside of bears though….

Bear Butt... Jerk

Bear Butt… Jerk

So what did we learn?  We learned that you should never place novel items in the woods with bears.  We learned that if you do this, bears will make sure to mess with your equipment, chew on your cameras, and rip apart your wooden stands… We also learned that bears are really really strong!  We learned that bears are really fuzzy…

Fuzzy Bear Legs. ... jerk.

Fuzzy Bear Legs. … jerk.

I learned that I would have done things differently.  If I were to do it all again (which I probably will), I would move all of the cameras to a nearby tree instead of a wooden stand.  After four weeks of bears being jerks, this is exactly what I ended up doing.

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.

Bear and Camera Cartoon

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Wrapping Up A Great Field Season

As the days are getting colder, snakes are slowly making their way back to their dens.  My technicians are still tracking their progress, but little-by-little each of our 15 radio-tagged snakes are getting closer to the location where they will spend their winter sleep.  This summer was a huge success as we collected ecological data for our rattlesnakes in our pre-burned habitat.  Much of this success was made possible due to a great team of technicians: Alyssa Hoekstra, Andrew Brown, Zack Maisch, Alex Dyson, and Mark Herr (lab undergrad extraordinaire)!

Our snakes led us to some great data this past summer.  Males did not disappoint us, and they typically had us hiking over large tracts of land. Sometimes, males were able to travel over 1-km in 24 hrs, up and over large mountains.  Much of this traveling was to find receptive females, and we observed many mating encounters as well as male-male combats!

Male and Female Timber

Large male (black phase) wrapped around a female (yellow phase). Typically males will follow females and attempt to entice her to mate by rubbing his head along her body. This female obviously didn’t want to play those games and just remained coiled. (Photo by A. Dyson)

Females stayed a little closer to the den sites and study area. The females main concern was foraging for food, but sadly none of our females at the main study site were gravid this year. Given the high abundance of chipmunks and mice throughout central PA this summer, I would not be surprised if many female rattlesnakes were gravid next summer.  It is believed that good reproductive years for timber rattlesnakes typically follow good food years.  Although we were not measuring small mammal abundance last year, I suspect it was lower than this year. Following the conclusion of our project, we may be able to shed some light on this relationship between rattlesnakes and their prey.  Additionally, prescribed fire can enhance small mammal abundances, which may lead to increased reproductive rattlesnake fitness!

Rattlesnake Eating Chipmunk

Rattlesnake consuming a chipmunk… Alvin!!!! (Photo by Z. Maisch)

In addition to following the snakes around, we also took some time to characterize the pre-burn study sites and the available resources for timber rattlesnakes.  We measured small mammal abundances, operative temperatures, available vegetation, and acorn mast production.  We will compare these available habitat characteristics to next year’s to see how these variables change based on year-effects and the prescribed burn.

chipmunks in tomahawk

Two chipmunks captured in a Tomahawk trap. Each small mammal receives an ear tag so we can identify it at a later data when it is captured again. This mark-recapture technique allows us to measure small mammal abundance throughout the study area. (Photo by A. Dyson)

In addition to the prescribed fire project, we also embarked on two new projects with the help of Tom Radzio!  Tom is a colleague from Drexel University, and he is using cameras to observe tortoise behavior outside of burrows in the southeastern United States for his dissertation.  Tom was gracious enough to loan us a few cameras so that we could embark on these great, new side-projects.

For the first side project, we are currently looking at the ecological trade-offs between thermal resource acquisition and predation at gestation sites of various sizes.  We collected some great data regarding potential predators, including black bears, bobcats, raccoons, and hawks.  Whereas we have already pulled all of our cameras from the field, we are still collecting data from these videos.  Currently, I have a great team of undergraduates assisting me with this process, including: Mark Herr, Michaleia Mead, and Tommy Cerri.  We hope to have all of these data collected and analyzed by the end of November!  We are predicting that we will see a higher amount of predator activity at more open, larger gestation sites, but we will also find higher quality thermal habitat at these same sites as compared to smaller, more enclosed gestation sites.  We are looking forward to the results!

Bobcat at Study Site

Bobcat walking through a large, open gestation site. Whereas the bobcat did not show any interest in the foam, rattlesnake models that we placed at the site, the mere presence of the predator suggests that an encounter is possible.

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A black bear attacking a foam model at an enclosed, smaller gestation site. The bear first approached two foam, rattlesnake models and swatted off their heads. It then bit two more models (one shown here) before taking off out of the gestation site.

For the next side project, Tom Radzio and I are looking at when rattlesnakes decide to go back into their dens, how this correlates with environmental temperatures, and if predators are attracted to these den sites during this time of rattlesnake ingress.  We are currently collecting data at these den sites and we have a great undergraduate, Tommy Cerri, who is assisting us with analyzing these videos.

Rattlesnake basking in front of a den site. If you look closely you can see some small grey iButtons recording environmental temperatures.

Rattlesnake basking in front of a den site. If you look closely you can see some small grey iButtons recording environmental temperatures.

This fall will be filled with a lot of data analyses, writing, and hopefully a few published results. Stay tuned as we finish up a few of these projects.  I will make sure to update everyone on the results to each of the finished products.

Field work in action! Me capturing a small timber rattlesnake. (Photo by T. Langkilde)

Field work in action! Me capturing a small timber rattlesnake. (Photo by T. Langkilde)

This post originally appeared on chowey.net!