The Lizard Log

The Langkilde Lab in Action


Leave a comment

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!


Leave a comment

Racing baby lizards (for science)!

In the latest chapter of the “bearded lady” saga (female fence lizards bearing ornamentation that is typical of males), we continue to investigate what potential advantages these “unattractive” females could have that allow them to persist in high numbers.

We know that in many species, colorful, conspicuous ornaments have a tight relationship with levels of particular hormones (such as testosterone), which themselves are related to physical performance. One of our current guesses is that even though females bearing male-like ornamentation are not prime sexual partners in the lizard world, their offspring might be more physically competitive than offspring of the more desirable females (read more here). The costs and benefits of both strategies could be responsible for the coexistence of the two!

A good way of measuring the physical performance of an animal is by how fast they can run. With the help of two enthusiastic undergraduate students, Maggie Zemanek and Sean Dailey, I am recording slow-motion videos of juvenile lizards running on a race track. This will help us calculate how fast each of them can run, and compare that to what their moms looked like: are the faster runners offspring of ornamented females?

img_20170221_131100

Do your best!

img_20170221_131145

Body temperature greatly influences performance in reptiles, so Sean makes sure we record how warm each lizard is

img_20170221_130931

Maggie sets a contestant on its marks

Maggie, Sean and I still have a lot of juvenile lizards to race, but hopefully we’ll find some interesting patterns in our experiment. Stay tuned!


Leave a comment

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.

 

male-and-female-timber

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.

canopy-pics-between-color-morphs

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!

OLYMPUS DIGITAL CAMERA

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


1 Comment

Rattlesnake Research Round-up

One in a continuing series of posts highlighting the work of undergraduate researchers in the Langkilde Lab.

Michaleia Mead

My name is Michaleia Mead, and I am a senior in Wildlife and Fisheries Science, Wildlife Option. This is my first year working in the Langkilde Lab.  I spent the summer 2015 working for the lab on maternal stress of Eastern Fence Lizards.  But currently, in my research under Dr. Chris Howey, I am looking at ecological trade-offs between thermal quality and risk of predation at timber rattlesnake (Crotalus horridus) gestation sites.  A gestation site is the area that a female snake spends the duration of her pregnancy in from early spring, and throughout the summer to parturition (birth of the litter).  These sites typically receive a good deal of sunlight and allow the female to maintain an elevated, preferred, body temperature.

DSCF5533

An adult female found basking at a gestation site later in the year.

DSCF5572

A neonate rattlesnake found at a gestation site.  Note the size of the neonate as it is hiding under a small birch leaf.  Neonates will typically remain at the gestation site for about 1 week, basking in the sunlight, prior to following their mother to a nearby den site.

The “openness” of gestation sites range from very open to densely forested sites, enclosed by many tall trees.  For this study, we identified three sites that were very open and three sites that were more enclosed.  We compared the canopy openness, thermal quality, and risk of encountering a predator between these two types of gestation sites.  In particular, we are comparing the relationship between site openness and thermal quality as well as site openness and the probability of timber rattlesnakes encountering a predator.  Thermal quality is the amount of time that the range of temperatures a rattlesnake prefers overlaps with the temperatures that are available (thermal quality would be better at a site if it provided more time when available temperatures overlapped with preferred body temperatures).  I am testing the hypotheses: 1. Thermal quality of the open sites would be better due to a greater percentage of time that the available temperatures would exceed preferred temperatures, and 2. Risk of encountering a predator would increase as site openness increases.  

Cameras were placed at each of the six gestation sites to monitor rattlesnake behaviors and occurrence of potential predators traveling across gestation sites, despite the fact that bears sometimes take our cameras out…jerks.  We also placed biophysical models at each gestation site to measure the available body temperatures at those sites. Via these cameras, I’ve observed potential predators and also documented potential food sources for the rattlesnakes, such as chipmunks.  We’ve determined that open gestation sites are in fact warmer than more enclosed gestation sites, and the thermal quality of these sites is better.  The improved thermal quality of these open gestation sites may lead to shorter gestation times by gravid females, more successful reproductive bouts, and increased population health.  Contrary to our second hypothesis, we do not see more predators at more open gestation sites; however, we do see more predators as the overall area of the site increases.  This suggests that we may increase the openness of gestation sites in order to improve thermal quality for rattlesnakes, and, as long as we do not increase the overall open area on the ground, risk of encountering a predator should remain constant.  All of the data have not been analyzed, but they are showing signs of supporting the first hypothesis.  I am currently working on writing a manuscript for these data and should be completed sometime in late January.

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.

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.

Tommy Cerri

My name is Tommy Cerri, and I am currently a senior biology major. This is my 3rd year working in the Langkilde Lab. My current research working with Chris Howey focuses around the behavior of rattlesnakes and relationship these snakes have with predators in the community while entering into their den (referred to as ingress). The main objective of my study is to observe rattlesnakes of varying ages entering and exiting rattlesnake dens and the relationship these behaviors have with the occurrence of predator visits at those den sites. For this study, we are predicting that:

  1. Adult and juvenile rattlesnakes will arrive to the den before neonates
  2. Predator visits will increase as more snakes begin to enter the den
  3. Snake activity in front of the den will increase positively with environmental temperature and decrease when temperatures drop, and
  4. Snakes will retreat to the den as predators approach.

This research is proving to be important to the scientific community because we are beginning to see some behaviors that have never been documented before.  For example, we are finding that rattlesnakes are very active around the den for at least a couple weeks prior to hibernation.  Additionally, prior to exiting the den, rattlesnakes appear to stay under the overhang of the den and observe their environment.  We are unsure if this observation behavior is to test the thermal characteristics of the environment or to look out for predators.  In addition to this, the study may provide insight into what snake age is the preferred prey of predators within the community.  Snakes varying in age from neonate to juvenile and adult have all been seen coming in and out of multiple den sites that have been studied via different cameras that have been set up facing four different rattlesnake den sites located throughout Pennsylvania and New York.  From these cameras, we are able to see predators that visit the den as well as the behavior of rattlesnakes as they enter and exit the den during the day. While collecting data, this is what the view of the den from the camera looks like.

Trailcam2

Can you spot the rattlesnake in this picture from one of our trail cams?

Trailcam1

In this case, the rattlesnake is only a few feet from the mouth of its den.

In the pictures above we are actually able to see two adult rattlesnakes basking right outside two of the den sites under question. While right now the study is still in its preliminary phase of data collection, we have already observed some interesting trends between snake activity and temperature.  For example, snakes tend to be active outside of the den during both the day and night until ambient temperatures reach a specific threshold (roughly 42 degrees F).  Some of these activities appear to be basking behaviors, however, night time activities are unknown.  As of right now, we are not seeing any trends between predators and specific age-related prey choices, and we have not recorded any predation events. We hope to be finished data collection by the end of December and have a paper reporting the results completed by May.

Stay tuned, as we’ll publish a follow-up here with our official results!


Leave a comment

Closing the Never-ending Loop

One in an occasional series of guest posts by Langkilde Lab alumni:

Hi Everyone!

My name is Jill Newman, and I’m a Langkilde Lab alumni. I came to the lab as a Research Experience for Undergraduate (REU) student during the spring and summer of 2012. During my six-months with Tracy’s lab, I did some cool things including working on several different graduate student projects, co-authoring seven manuscripts, and exploring a state that I never really saw myself going to: Alabama. It was a really unique opportunity that I was able to experience as an undergraduate student!

I graduated from Northeastern University in Boston, MA in August 2013. Northeastern likes to boast that 90% of its graduates become employed or enrolled in graduate school 9 months after graduation. Feeling the “pressure of being a statistic” on my shoulders, I applied to tons of jobs and explored the option of graduate school. After 8 months of painful unemployment, I became one of Northeastern’s “90%-ers” when I accepted my first field technician job out of college.

Down on the Florida panhandle, Virginia Tech works with an interesting species of amphibian called the reticulated flatwoods salamander. Listed as Endangered by the USFWS, reticulated flatwoods salamanders are a species of interest because they are very dependent on their habitat (longleaf pine, ephemeral wetlands, and likely fire suppressed areas). Virginia Tech’s study is looking at metamorph and adult movement to and from breeding ponds. As an amphibian tech, I surveyed for these salamanders using drift fences/funnel traps. I captured, measured, VIE-tagged (basically giving salamanders a tattoo!), and PIT-tagged salamanders for a multi-year mark-recapture study.

Reticulated flatwoods salamander (5)_cropped 3

Reticulated flatwoods salamander (Ambystoma bishopi)

In my opinion, many of the “cool” herp jobs are down South because the southern states have a much wider diversity of herpetofauna. However, when an opportunity to work in the White Mountains of New Hampshire arose, that was very difficult to turn down! For this project, we were interested in looking at species dispersal and species interactions in an aquatic system. We conducted stream salamander surveys in which half of the streams were known to have brook trout and half of them did not. We captured, measured, and VIE-tagged salamanders for a mark-recapture study. For more information about this project, check out the Lowe Lab!

Wood frog, Lithobates sylvaticus

Wood frog, Lithobates sylvaticus

Spring salamander, Gyrinophilus porphyriticus

Spring salamander, Gyrinophilus porphyriticus

Immediately following my New Hampshire job, I was rehired by Virginia Tech to go back to Florida to work on their gopher tortoise project. The gopher tortoise is a keystone species in the Southeastern U.S. because it digs burrows that provide shelter for over 300 other species! However, USFWS has this species listed as Threatened for reasons including habitat loss, pet trade, human consumption, relocation, and disease. For this tech position, we used occupancy models to survey gopher tortoise populations where their population is known to be in heavy decline. We also used camera traps to check gopher tortoise burrows for activity levels and for commensal species.

[Funny thing about this job: after three months of actively looking for tortoise burrows, I NEVER ONCE saw an actual tortoise while in the field! The only one I’ve seen in the wild was working for Tracy!]

Juvenile gopher tortoise, Gopherus polyphemus, caught on camera trap eating a leaf outside of its burrow

Juvenile gopher tortoise, Gopherus polyphemus, caught on camera trap eating a leaf outside of its burrow

Eastern diamondback rattlesnake, Crotalus adamanteus, redemption picture...make sure Sean Graham sees this!

Eastern diamondback rattlesnake, Crotalus adamanteus, redemption picture…make sure Sean Graham sees this!

Another really unique opportunity that I had was working for the Smithsonian Conservation Biology Institute Wood Turtle Ecology Department. Wood turtles are endemic to North America and are listed as an endangered species. These turtles obtained their conservation status as a result of habitat destruction, agricultural accidents, and road traffic. I had the opportunity to stream survey and radio-track these turtles as part of a 20-year-long mark-recapture study. We tracked male and female turtles as they made large movements across landscapes. This is important for management purposes because over the course of these “large movements,” turtles will occasionally change watersheds (making it imperative to protect multiple watersheds).

Wood turtle, Glyptemys insculpta, shell

Wood turtle, Glyptemys insculpta, shell

An older wood turtle known as “Gramps”

An older wood turtle known as “Gramps”

Sometimes as a field tech you feel like you’re in this “never-ending loop” of traveling around every few months and constantly meeting new people that you may never see again. It can be very difficult at times but there is a lot to gain from these types of jobs. First, you gain important wildlife skills that prepare you for graduate school (if you choose that route), and second, you have the chance to network with great people from all across the country. It’s a challenging but often necessary step before entering the field of wildlife biology.

In my case, the diversity of experiences from my undergraduate and technician positions have paid off. This fall semester, I’m joining Dr. Kyle Barrett of Clemson University to pursue my Masters of Science in Wildlife and Fisheries Biology. My thesis is still in the works, but I will be surveying target herpetofauna in the Blue Ridge Mountains of South Carolina for the South Carolina Department of Natural Resources. This is a great opportunity for me to apply skills that I’ve learned in my past field experiences. Additionally, it’s also a fantastic way for me to learn new skills in the field and classroom. Furthermore, I am also very excited for my first college football game (no offense, Northeastern)!

My opportunity with the Langkilde Lab opened many doors for me when I graduated from college. I’m very appreciative of the chance and great honor to have been an REU student in this lab, and I really enjoyed working with Tracy and all of her graduate students! I would highly recommend that all undergraduate students do an internship/co-op/REU if possible. The more experience you can get earlier on in your career the better off you will be!


Leave a comment

Studying and Staying Sane

The researchers in our lab have many interests, not all of which are related to science. In this post, undergraduate Tommy Cerri describes his preparation for the MCAT…as well as other actives that help him stay sane. 

Spring 2015 has been one of the most hectic semesters for myself. My time is split between working in the lab, being a full time student, and studying for the MCAT. I plan on taking the MCAT exam this summer in June, and the studying process so far has been grueling. Here is a picture of my study materials I got in the mail earlier this semester. A total of 9 books that I have to get through in only a few short months.

mcat

As of April this year, the format for the medical school admissions test has been changed. Most importantly, it is no longer a test of about 4 hours, it is a test that runs about 7 hours. This means they added biochemistry, sociology, psychology, as well as a few other topics that will be tested on the exam. Either way my studying has been going swimmingly, and I continue to study on a daily basis hoping for the best (fingers crossed)!

Due to this huge time commitment, my participation in the lab has not been as big as I would have hoped. I do help out though! As of late, I have picked back up where I left off last semester assisting Gail with lizard behavioral videos. I do enjoy these videos: the lizards are extremely active, which can be quite amusing. A few other miscellaneous tasks have come up within the lab and I love helping out with whatever needs done when I have the time.

Outside of lab I have given a handful of tours for prospective Penn State students. Don’t worry, I always give the Langkilde Lab a shoutout on each of the tours. Many times the parents are very interested about the research we do in the lab and I am always happy to fill them in on all the amazing things we are all doing! Parents of prospective science students are always intrigued by the potential research opportunities we have to offer here at Penn State, and I love to talk about some of my awesome experiences I have been presented with. The students always get a good laugh when I tell them I fed crickets to lizards once a week when I was a freshman.

In other news I did score 2 goals in my most recent intramural soccer game last Monday, and my team won our IM basketball game as well! Club sports might be on the horizon of my senior year, who knows…


1 Comment

Don’t Prey on Me: Part 1

By Mark Herr

Imagine you’ve passed your deadline for filing a report at work. The report isn’t finished and now you need to decide where you’re going to finish it. This is critical, because your boss hasn’t confronted you about it yet, and you just might get off scot-free if you manage to get it in soon enough. Here is the dilemma: If you work from home, you won’t see your boss and so won’t get a thrashing. Without running into you, your boss might not even recall the fact that you were supposed to submit the report, and you’ll get off free and clear. Your job fully permits you to work from home, but unfortunately you don’t have access to all of the company resources you need to get it done as efficiently as possible. It might take twice as long to finish from home, and if your boss already knows it’s missing you are going to be in even more trouble if it’s extra late. If you go into the office you’ll be able to finish the report in half the time and might get it submitted before anyone realizes it’s missing, but you’ll also risk the thrashing from your boss if he is aware. This is the type of situation that people encounter all the time: problems with multiple solutions, each with positives and negatives and no clearly superior alternative.

It just so happens that scenarios like these are common in nature as well, and how organisms respond to problems like these has important impacts on ecology and evolution. When we discuss the ways that organisms respond to problems like these, we refer to them as trade-offs: situations where an individual, population, or species gives something up in return for something else. It seems simple enough, but it turns out that this concept is tremendously important. For example, if a predator inhabits a landscape with diminishing prey resources, it may face a trade-off in how to respond. Some individuals may become more active in order to find more prey to sustain themselves, while others may take the opposite route and stop moving in order to conserve what energy they do obtain. In this way, a trade-off like this could result in one species diverging into two – an active forager and an ambush hunter.

This brings me to the research project that I’m going to be working on this upcoming spring and summer. I’ll be working with lab post-doc Chris Howey, who’s currently studying the way that proscribed fire impacts Timber Rattlesnakes here in PA. Chris is particularly interested in the impacts that these fires have on gravid (pregnant) female rattlesnakes.

So while I’ll be working with Chris helping him out on his larger project, we’ll also conduct a side project on the trade-offs that gravid female rattlesnakes make during the active season. Shortly after emerging from their winter dens, gravid female rattlesnakes will congregate in open rocky areas to incubate their developing embryos. Typically they stay at these spots, termed gestation sites, for nearly the whole active season – until they give birth to live young sometime in late summer. They are spending their time thermoregulating in order to develop their embryos as efficiently as possible, so it’s obviously important for them to choose sites with good thermal qualities.

This is where they might encounter a trade-off, though. The largest, most open rocky areas will have the most sun exposure, and so one would think they would be the best places for the snakes to choose as gestation sites. However, we think that these sites might leave the rattlesnakes even more exposed to predators than they would be otherwise – this is especially important because the snakes are already more vulnerable while out basking than they would be if they were foraging in the forest where their camouflage is most effective.

This past summer we found that some pregnant females chose smaller, more closed canopy spots with less sun exposure as their summer gestation sites. Why would these rattlesnakes be choosing sites like this when big open sunny spots are available? We think that this might be a classic ecological trade-off: with snakes weighing the thermal quality of the spots with the risk of being attacked by predators.

Gadsden_Prey copy

This rattlesnake is doing a terrible job of trying to avoid predators.

This might be what’s going on, or it might not. Perhaps the snakes are just choosing the spots that are closest to where they denned up. Maybe the closed spots and the open spots don’t even have different predation risks attached to them! We’re interested in exploring this issue to see if this is really what’s going on, and understanding this dynamic might help conservation authorities understand the ways that a species under threat (like timber rattlesnakes here in the Northeast) use the different parts of their habitat.

In order to test to see whether a trade-off really is occurring, we’ll be assessing the different gestation spots chosen by rattlesnakes for their thermal qualities and predation risk. To test the thermal quality we’ll analyze the sun exposure of these sites and we’ll place thermal models designed to mimic rattlesnakes and analyze them against the preferred body temperatures of live rattlesnakes that we measure in the lab.

How will we measure predation risk? This is the part that I’m working on right now in preparation for this summer. We are making realistic foam rattlesnake models that we are going to set out at the different sites. The foam that we are casting the snakes in should hold the imprint of attack from the predators and should give us some idea of what type of predator went after our snakes! This is a technique that’s been used before (on rattlesnakes no less!) by Vincent Farallo to quantify the risk of predation, and we are excited to use it to test our hypothesis!

Making these foam models is taking up most of my time on this project right now, and we are going to need a couple hundred by the time spring starts, so I’m busy! I’ll post more updates on the project here on the Lizard Log in the future as we get rolling – but I’ll leave you off with some photos of the model making process that’s taking up my time now while there’s still snow on the ground!

The first step in making our models is to get an actual snake to cast them from! We took this preserved timber rattlesnake specimen from the teaching collection here at Penn State to make our mold for the future specimens.

The first step in making our models is to get an actual snake to cast them from! We took this preserved timber rattlesnake specimen from the teaching collection here at Penn State to make our mold for the future specimens.

Then we posed her in a typical basking rattlesnake position – getting the snake like that isn’t as easy as it seems! When specimens are fixed in formalin during the preservation process it tends to make them rigid and tough to work with, but we managed!

Then we posed her in a typical basking rattlesnake position – getting the snake like that isn’t as easy as it seems! When specimens are fixed in formalin during the preservation process it tends to make them rigid and tough to work with, but we managed!

After this we poured a rubber mold compound in the tray and let it set, then we removed the preserved snake and voila – snake mold!

After this we poured a rubber mold compound in the tray and let it set, then we removed the preserved snake and voila – snake mold!

Here you can see we’ve just poured the mixture into the mold – it will then quickly expand to fill the whole mold and once it hardens...

Here you can see we’ve just poured the mixture into the mold – it will then quickly expand to fill the whole mold and once it hardens…

We’ve got our rattlesnake model! The only step after this is painting it to make it look like an actual basking rattlesnake!

We’ve got our rattlesnake model! The only step after this is painting it to make it look like an actual basking rattlesnake!

Here’s a painted model, painting them is by far the most tedious part of the process – as the rattlesnakes have pretty intricate patterns. By the start of the project I’m going to need a couple hundred of these things painted and ready to go. It’s gonna be a busy semester!

Here’s a painted model; painting them is by far the most tedious part of the process, as the rattlesnakes have pretty intricate patterns. By the start of the project I’m going to need a couple hundred of these things painted and ready to go. It’s gonna be a busy semester!