The Lizard Log

The Langkilde Lab in Action


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Vernal Pool Macro-invertebrates in a Burnt Landscape

My name is Richard Novak and I am finishing up my freshman year. I am in the Schreyer Honors College and I am studying Wildlife and Fisheries Science, with the Fisheries option. This is my second semester working in the Langkilde Lab. In fall 2017, I began working under Dr. Chris Howey as a research assistant helping with rattlesnake gestation site video monitoring. Currently, Dr. Howey and I are working on a study with macroinvertebrate communities in vernal pools and how they are impacted by prescribed fire. I was fortunate to receive an Erickson Discovery Grant which will allow me to continue working on this project into the summer. So far, I have developed my research questions and data collection methods, and I have been gathering data throughout spring semester. This research experience has been valuable to me for several reasons. First, I have been able to get a first-hand look at the entire experimental design and execution process, something I can only read about in classes. Additionally, interacting with graduate students and other faculty has been very influential when thinking about my future ambitions and career path potentials.

Vernal Pool within a previously burnt landscape

Vernal Pool within a previously burnt landscape

The purpose of this study is to compare macroinvertebrates communities in vernal pools with varying fire histories.  Fire is being used as a forest management tool, which will create a more open landscape that some wildlife species may prefer.  Additionally, these prescribed fires may promote the growth of new vegetation and increase food for wildlife within the forest.  I am looking at water samples from 12 vernal pools; three that were burnt over once (in 2016), three were burnt and mowed over (in 2016; this is an additional disturbance to the landscape), three pools burnt over twice (in 2014 and 2016), and three vernal pools from a control group with no recent fire or disturbance history.  Specifically, I would like to answer the question, “do prescribed fire practices alter the macroinvertebrate communities of vernal pools?” This question has been relatively unexplored in previous research.  But preliminary data collected by Chris suggests that physiochemical (physical and chemical) characteristics of these pools are different, which could lead to differences in what macroinvertebrates are able to survive in these pools.  I will analyze water samples collected from these vernal pools for macro-invertebrates, identify all macroinvertebrates found to family, and determine abundance of each family. The water samples that I have been going through now were collected in 2016, and additional samples will be analyzed from 2017 that are currently being collected.  I look forward to getting out in the field this summer and assisting with measurements and collections.

Macroinv lab bench set up

This is what my lab bench typically looks like while I’m collecting data. My sorting tray with a sample spread out to the left, a hand-held magnifying glass, dissecting microscope, and the computer with my spreadsheet in the background. Note, there are also plenty of macroinvertebrate books to help me identify everything I find.

 

When I first began this project, I had to learn how to identify the macroinvertebrates to family. One of the reasons I am interested in macroinvertebrates is because of my interest in fly fishing, which requires basic knowledge of aquatic entomology, so I had some ID skills to bring to the table. I practiced using dichotomous keys to identify the specimens, a task I found time consuming but very learnable with practice. Now, I am very familiar with the families that I encounter most often. As of right now, I have identified the presence of over 20 families of macroinvertebrates among the vernal pools in the study. I find a lot of mosquito larvae (Culicidae), phantom midges (Chaoboridae), cased caddisflies (Limnephilidae and Odontoceridae), as well as several families of dragonfly and damselfly. To me, the coolest creatures that I find are fairy shrimp (Chirocephilidae) and water-boatmen (Corixidae) although I don’t come across either of those frequently.

Culicidae Pupae

Culicidae pupae. These will grow up to become the dreaded mosquito!

Chaoboridae Larvae

Chaoboridae larva. These are also known as phantom midges.

Chaoboridae Larvae

Limnephilidae larva. This is a type of caddisfly.  Caddisflies are known to build these ‘houses’ out of sticks, leaves, and rocks within their environment.  The actual larva is within this house made of sticks and you can see its head sticking out of the top.  Different species of caddisflies will use different substrates to build their houses, so you can tell species apart based on the house materials.

Limnephilidae

Odontoceridae larvae. These are another species of caddisfly. You can see that they use a different substrate material for their houses.

Chirocephilidae Larva

Chirocephilidae larva. This is also known as a fairy shrimp and can be very common in many of Pennsylvania’s vernal pools.

Corixidae

Corixidae adult. These are also known as water-boatmen. They are typically seen swimming across the surface of a vernal pool, but can dive to the bottom when foraging or escaping a would-be predator.

 

So far, I am finding more mosquito larvae (Culicidae) in unburned pools.  But among the burned pools, I am observing more mosquito larvae and caddisflies (Limnephilidae) in pools that were more disturbed (burned and mowed).  This trend among the vernal pools is interesting, because that mow was an extra disturbance on top of the burn, yet these two families appear to be doing better in these pools.  Please note though, these data are still being collected and these results may not accurately represent our final findings once we have analyzed all water samples.

Macroinv prelim data

Preliminary data for our macroinvertebrate communities within the four different treatments. In the future we will compare species diversity and richness among vernal pools. We will also see if there are any correlations between species presence/absence from vernal pools and the physiochemical characteristics of those pools.

Working on this project has been useful to me for many reasons. I have had a lot of fun sorting through samples and looking at the macroinvertebrates; it really never gets old to me which is good because I’ll be staring at trays a lot more this summer. It has been very satisfying to see my very own data begin to build on the spreadsheet as I work. Also, being around other lab members has given me a look into what school is like for graduate students. My freshman year is coming to a close, and I hope to take on new and exciting projects throughout the rest of my undergraduate career. When I came to college last fall, I did not expect to become involved in research right away, but I am very glad I took that step early and I have been fortunate in the opportunities presented to me. After graduating, I plan to pursue at least a master’s degree in a biology related field. I am interested in working for a natural resource management agency, although this experience has opened my eyes to the possibility of university research as a career. Whatever happens, my goal is to continue exploring more about biology and the organisms that fascinate me so much.

Richard Novak

Me looking hard at work keying out macroinvertebrates!


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Basking Site Use by Timber Rattlesnake Morphotypes – By Shawn Snyder

My name is Shawn Snyder and I am currently a senior majoring in Wildlife and Fisheries Science.  This is my first and only year working in the Langkilde Lab.  During the summer of 2016, I worked under Dr. Chris Howey as a Research Technician studying the effects of prescribed fire on timber rattlesnake populations.  This position provided me the opportunity to radio-track timber rattlesnakes, record habitat data on tracked snakes, catch new snakes (extremely fun), learn how to safely tube a venomous snake (even more fun), and conduct vegetation surveys.  Also, this position provided me the opportunity to formulate my own scientific question to test! Together, Chris and I thought up a small side-project that I could conduct throughout the summer, which provided me the fantastic experience of going through the scientific process, collecting my own data, analyzing those data, and now writing a manuscript so that I can share those results with the scientific world.

When we first started collecting data for my side-project I was a little apprehensive.  Once the data was collected and analyzed I realized that this project was going to take time and a large amount of effort to complete.  As the process of analyzing the data and then coming up with a plan for the manuscript began to take shape, I started to feel challenged and nervous by this new task. But weekly meetings with Chris to discuss the process of writing a manuscript have helped immensely.  This is my first manuscript and yes it is challenging, but it will all be worth it once we have a finished product. I have ambitions to continue on to a Graduate program after I graduate and this manuscript will help me build my C.V. to apply to Grad schools.

yellow-and-black-morphs

Two yellow morphs bask alongside three black morph timber rattlesnakes at a gestation site. Although we did not use gestating (i.e., pregnant) females as part of this project, this shows you the posture of a basking snake and the difference in color morphs.

My research is investigating if the two distinct morphotypes of timber rattlesnakes (a dark, black morph and a lighter, yellow morph; see above picture) use basking habitat with differing amounts of canopy openness and solar radiation. Previous research suggests that the dark morph evolved in response to thermal limitations in the northern parts of its range.  Darker snakes have more melanin in their skin, which allows them to absorb more solar radiation and maintain a higher body temperature than yellow morphs.  Yellow morphs having this thermal disadvantage, in theory would have to choose basking sites that receive more solar radiation to compensate for this limitation if they wanted to maintain a similar body temperature to the black morphs.  Specifically, I am testing the hypothesis that yellow morphs use basking habitat that has more canopy openness and receives more direct solar radiation (i.e., sun) than basking habitat used by black morphs.

 

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A black morph male timber rattlesnake is seen courting a basking yellow morph female.  Once again, the difference in color morphs is striking and has led many to ask what selective pressures are maintaining this polymorphism.

To test this hypothesis, I measured canopy openness over basking yellow and black morphs. I used the timber rattlesnakes that are being radio-tracked for Dr. Howey’s main study as my sample population and placed a flag where a snake was found exhibiting basking behaviors (see picture below  for example).  We took a picture facing skyward directly over the snake using a camera with a fisheye lens.  This lens takes a picture of 180 degrees and captures an image of all of the canopy over the snake (see picture).  We can then analyze these hemispherical photographs using a computer program called Gap Light Analyzer to measure the percent canopy openness and the amount of direct solar radiation transmittance (i.e., rays of sunlight) for each basking site.  Direct solar radiation is when the sunlight reaches the forest floor with no obstructions from the canopy; as opposed to indirect solar radiation which may be radiation that is being reflected off of clouds, trees, or the ground itself.  Our study site is characterized as having a mature Oak/Maple forest with an abundance of closed canopy throughout the area.  Both morphotypes use this “closed canopy” forest throughout the summer as foraging grounds, and when they need to bask they must seek out areas where some sunlight is making its way through the canopy.  This is where my question becomes very important comparing the habitat used by each morph.

 

flagged-yellow-morph

A flag is placed next to a basking yellow morph.  An exact description of the habitat is recorded so that I can come back at a later time (when the snake is not there) and take a photo of the canopy directly over where the snake had been.

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Two examples of hemispherical photographs taken over two different basking timber rattlesnakes.  Both canopies actually have similar canopy openness, but the canopy on the left receives far more direct solar radiation based on the placement of those canopy openings.

So far, my results show that the two morphs use habitat that have similar percent canopy openness, however, there was a difference in the amount of UV transmittance between the basking sites used by the two morphs.  Canopy openness doesn’t necessarily designate a “warmer” site because the sun path may not go directly over the gaps in the canopy of that site, thus, the site wouldn’t receive large amounts of direct solar radiation.  Black morphs use basking sites that received lower amounts of direct sunlight.  They may be able to do this because the greater amount of melanin in their skin provides a greater ability to absorb whatever direct or indirect solar radiation is available more effectively. Yellow morphs use basking sites that received more direct solar radiation.  They could be forced to use these sites to compensate for their disadvantage in their thermal ability.  I am currently working on writing a manuscript for these data and hope to have it completed by the end of 2016.  Stay tuned for more on this manuscripts progress!

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Here is a picture of Shawn (holding a Hellbender!!) while on a break from collecting some amazing data.


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Efficacy of Daylighting… Part I

Pregnant female rattlesnakes prefer to maintain an elevated body temperature (~32 °C), which allows for a more optimal development of embryos.  In Pennsylvania forests, however, these warm temperatures are not very abundant.  So, in order to achieve these elevated body temperatures, pregnant females seek out rare, open habitat (known as gestation sites) that receive a lot of sunlight.  Sometimes, females may travel up to a mile from their den sites just to gain access to openings within the forest canopy.

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Yellow morph female timber rattlesnake sits coiled under a small rock overhang.

However, not all open gestation sites are created equally.  Last year, Mark Herr, Michaleia Mead, and I uncovered a trade-off at timber rattlesnake gestation sites of various sizes.  Gestation sites that were very open provided pregnant females with more sunlight and warmer body temperatures for a longer duration of the day.  But, these same sites also came with an increased risk of predation!

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At a timber rattlesnake gestation site, a red-tailed hawk swoops in on top of a foam timber rattlesnake model (not seen). A yellow-morph timber rattlesnake model is pictured behind the hawk.

More predators visited these more open sites, predators like bobcats, fishers, and hawks.  But, smaller, more enclosed gestation sites were so thermally poor, we observed females returning to their den at the end of the field season still pregnant!  The use of thermally unfavorable gestation sites may provide the rattlesnake with a sanctuary from potential predators, but there are still terrible repercussions for choosing to use these sites.  We have found that snakes using thermally unfavorable sites tend to give birth at a later date.  The timing that an animal gives birth is very important.  If rattlesnakes give birth to their offspring too late in the year, the small neonate offspring will have little, to no time to complete their first shed and then obtain a small meal before entering the den for hibernation.  It is believed that survival for neonates unable to do these two things is close to zero.  Further, some pregnant rattlesnakes that use thermally unfavorable gestation sites are known to abort their entire litter toward the end of the summer if she decides that they are developing too slowly.

So why would pregnant females continue to use small, more enclosed, thermally poor gestation sites?  Possibly because there was a decreased risk of predation?  Possibly, however, because of strong site fidelity?  Possibly these sites were, at one time, thermally favorable, but over the years vegetation has encroached upon these open areas and shaded out the once warm, sunny rocks.  Due to the rattlesnake’s fidelic response to locating a favorable gestation site, they now find themselves sitting among the shade throughout much of the day.

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Timber rattlesnake taking advantage of a small break in the canopy and some sunlight reaching the forest floor.

 

We’ve addressed the problem, now how do we fix it?

In order to manage timber rattlesnake populations better, forest and wildlife managers have begun to open up gestation sites, un-shading these areas from vegetation, in a process called “daylighting”.  However, recall that more open sites have an increased risk of predation.  So can we open up these sites just enough to let the sun in, but keep the hawks out?  In an attempt to suppress the increased risk of predation that we observed at more open sites, I have begun to direct daylighting techniques to target specific trees that would increase the amount of solar radiation a site would see, without greatly increasing the risk of predation.  To do this, I will use hemispherical photography (see picture below), observe the path of the sun throughout the gestation period, and then target those trees that overlap with the path of the sun.  This way I can open up each of the sites just enough, but keep those trees that do not overlap with the path of the sun and could perhaps maintain some decreased risk of predation.

hemispherical-sun-path

Hemispherical photograph at one of our gestation sites. The path of the sun throughout the entire gestation period is shown by the yellow arc. Trees that overlap with this arc can be targeted to improve the thermal quality of the site.

Of course I want to address this management idea with as much scientific rigor as possible for an ecological study.  This past summer, I visited six historic gestation sites within Pennsylvania.  Four out of the six sites are pretty shaded over, and I consider thermally poor.  Two of the gestation sites are fairly open and should provide pregnant females with a plethora of sunlight.  This summer, I surgically implanted nine pregnant timber rattlesnakes with temperature-sensitive radio transmitters, which allowed me to track these individuals throughout the summer. I followed each snake and noted their behaviors, body temperatures, and the date that they gave birth to their young.  Additionally, I measured available body temperatures and risk of predation just like we did in the previous experiment that Mark, Michaleia, and I completed last summer.  The catch is, this winter I will go into three of the six sites (along with US Forestry personnel), and we will remove specific trees blocking out the path of the sun.  Then next summer I will repeat everything and determine if Daylighting improved these thermally poor sites.  Will I see warmer available temperatures within the Daylighted sites?  Will snakes within these sites maintain warmer body temperatures and for a longer duration of the day?  Will these snakes give birth at an earlier date, allowing their young to shed and get a first meal before hibernation?  Will I still see an increased risk of predation?

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Biophysical models laid out at a gestation site and measuring the potential body temperatures that a snake could achieve at that site.

Many of these questions I won’t be able to answer until next year.  But, I am collecting some interesting data thus far.  As expected, the two sites that were more open did have warmer available temperatures.  Snakes occupying these sites maintained warmer body temperatures, moved less often, and were the first to give birth to adorable baby rattlesnakes!

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Neonate rattlesnake coiled up next its mother.

But, these sites were also visited by more potential predators.  In fact, in one instance we observed a red-tailed hawk swoop down and nab a garter snake that was basking alongside our pregnant rattlesnakes!

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Red-tailed hawk grabbing a quick dinner at a gestation site. I’m fairly certain this was a garter snake that got nailed.

The more enclosed sites were indeed cooler and snakes at these sites maintained cooler body temperatures and moved more often.  It appeared that some of these pregnant females shuttled between nearby sites in order to track the path of the sun.  In the morning the snake may be at one site, and in the afternoon that same snake would move to a nearby site.

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Female at a thermally poor area was typically found in the morning at a cut tree stump. In the afternoon she typically moved to another location.

Other snakes continued to move throughout the entire summer from one site to the next; constantly searching for a thermally suitable site where she could continue to develop her babies.  Unfortunately, all of these movements brought one of our mommas too close to a nearby road where someone swerved into the shoulder in order to run her over.  Although the loss of this mom was a little tough on me, it did show me just how important it is to improve these historic gestation sites.

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Our big momma rattlesnake could never find a suitable gestation site. She moved from potential site to potential site for about a month before coming too close to a nearby road.

Currently, as I am writing this blog, we are still waiting on some of our snakes from the thermally poor sites to give birth.  As we find neonates (babies) at each of our sites, I will also collect data on each of them so that we can compare body condition (health) among sites.

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Collecting data on newborn rattlesnakes is a fantastic way to start anyone’s day. I’m collecting data on body length and mass so that I can determine the body condition (or health) of each individual.

 

Next year, I will continue to track snakes throughout these same gestation sites.  However, following our daylighting management, we hope that all of our pregnant snakes will give birth at early dates, move less, and stay clear of predators.  To be continued…

 


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Uncovering the Effects of Prescribed Fire on Vernal Pool Amphibians

Fire is landscape disturbance that can do great things for resident organisms. Certain plants and animals are adapted to cope with or even thrive in the earlier successional habitat created by this blistering disturbance. Serotinous pine cones that open following a fire, oak trees with thick bark protecting them from the heat of the fire, or grasses taking advantage of the nitrogen released in the post-fire soil. Small rodents like mice and chipmunks dive into burrows to protect themselves from the direct effects of a burn, only to re-emerge in a scorched world that will be filled with food, grasses and acorns, within a year. Other species like snakes and lizards may survive the fire and find a new forest with more sunlight reaching the forest floor and greater basking opportunities. Forestry managers have begun to reintroduce this natural disturbance back onto the landscape in the form of a controlled burn. And whereas some species may benefit from this disturbance, other species may not fare so well to the disturbance itself or the post-fire landscape. For many species, it is unclear how they will respond to prescribed fire.

 

The effects of prescribed fire on vernal pools and vernal pool amphibians remains largely understudied.  Some amphibian species like Spotted Salamanders, Jefferson Salamanders, and Wood Frogs rely on vernal pools as an essential habitat where their eggs can be deposited and larvae can develop in the presence of a plethora of food and absence of fishy predators.  These pools disappear each summer only to refill with winter rain and snow melt, just in time for spring migrating salamanders and frogs which lay their eggs among their submerged branches and vegetation.  The eggs and larvae of amphibians can be highly sensitive to changes in water chemistry and temperature.  As fire changes the landscape around a vernal pool, it may also influence characteristics of a vernal pool. Reductions in forest canopy may allow more light to reach the vernal pool and increase amphibian larvae growth rates.  Run-off from the burnt forest floor may also increase alkalinity within the vernal pool.  Following a series of prescribed burns in Florida, Clay Noss and Betsie Rothermel found a slight increase in vernal pool water pH; however, this change did not affect their focal species, the Oak Toad.  So, would a similar change be expected from prescribed fires in the forests of Pennsylvania?  Would amphibians native to our vernal pools respond in similar ways to the Oak Toad?

 

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Jefferson Salamander eggs attached to a submerged branch.

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Wood Frogs mating within a vernal pool. Large swollen eggs are present in the background as well as a freshly laid egg mass to the right.

These are just a few of the questions that I am looking to answer with a couple research projects I began this spring.  Luckily, I have the assistance of a fantastic undergraduate, Michaleia Mead, who will stay on after she graduates this spring and turn some of these projects into her Masters thesis.  For our first project, we began sampling the water chemistry (pH, dissolved oxygen, conductivity), temperature, and physical characteristics of a series of vernal pools with differing burn histories.  We are also measuring the canopy cover over the vernal pools and the amount of UV-B radiation that may reach the water surface.  UV-B is known to cause detrimental effects on amphibians in high enough doses. We want to see if vernal pools in an oak dominated forest respond to prescribed fires in similar ways to the vernal pools of Florida.  We will sample invertebrate and amphibian abundance and diversity within these vernal pools.  Do we see a change in community composition of a vernal pool as characteristics are altered by prescribed fire?

 

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Vernal pool located in a post-burn landscape. This tract of land was burned in 2014. Note the charred trees in the background and reduction in understory vegetation.

To accompany the field projects, we began to raise Wood Frog tadpoles in the lab under different pH and UV-B conditions.  We will determine if these changes affect tadpole development and survival.  Additionally, we will compare corticosterone levels among tadpoles from different treatments to determine if certain treatments lead to more stressed tadpoles.  Even if tadpoles survive and develop under certain conditions, developing under stressful conditions can result in increased energy expenditures and decreased fitness.  This could have implications beyond the vernal pool if recently metamorphed Wood Frogs have lower energy reserves.

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50 tadpoles are placed in each tank with varying amounts of pH and UV-B.

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Our experimental set-up manipulates water pH and amount of UV-B exposure, while controlling room temperature.

So stay tuned as Michaleia and I update everyone on the progress of our studies!


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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!


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Underwood Prescribed Burn – A Taste Of Things To Come

Earlier today, I posted a blog which briefly discussed the projects that I will be conducting over the next two years.  Two projects are looking at the effects of prescribed fire on herpetofauna.  Yes, there may be direct effects as reptiles and amphibians may be caught up in the fire and may become injured or killed.  But, many reptiles and amphibians will survive the fire and have to deal with the changes in habitat.  But seriously, to what extent can a prescribed fire change the landscape?  What exactly does a prescribed fire/controlled burn look like in action?  My fantastic team of technicians will be assisting me this summer as we collect pre-burn data.  Most of them will never see an actual prescribed fire.  These are just some of the questions that may go through my technicians’ minds as they work for me this summer; some questions that may be going through your mind as well!  So today we took a field trip away from our field sites to see a prescribed burn in action.  After an 0800 briefing we set out to observe the burn in action.  Everything went as smoothly as we could have hoped for, and the burn snuck its way through the forest consuming  leaf litter, high-bush blueberry, low birch and maple saplings, and coarse woody debris.  Flame heights mainly stayed pretty low, and nothing got out of control.  Next summer my study sites will be burned as well, and we will be able to investigate the effects on timber rattlesnakes and vernal pool amphibians.  Can. Not. Wait.

The fantastic team of technicians - Alyssa Hoekstra, Alex Dyson, Zack Maisch, Mark Herr, and Andrew Brown (from left to right)

The fantastic team of technicians – Alyssa Hoekstra, Alex Dyson, Zack Maisch, Mark Herr, and Andrew Brown (from left to right)

The main method of igniting the fire was via 'drip torches' as being prescribed in this picture.

The main method of igniting the fire was via ‘drip torches’ as being prescribed in this picture.

Smoking landscape

Smoking landscape

Mark Herr posing with the fire

Mark Herr posing with the fire

Fire crew keeping control of the prescribed fire.

Fire crew keeping control of the prescribed fire.

Slow creeping fire.

Slow creeping fire.

Fire line making its way through the underbrush.

Fire line making its way through the underbrush.