A lot of my work in the lab involves assessing the health and well-being of our fence lizards under different conditions, including their parasite burdens. Parasite infestation can vary with immune status, stress, or external factors such as predation (for example, lizards in fire ant invaded areas have fewer ectoparasites). Ectoparasite (ticks, mites, etc.) load is easy to assess, as we count them on each lizard shortly after capture. Internal parasites are a bit trickier, but one method commonly used in veterinary medicine is to collect their feces, and check it for intestinal parasites and eggs.
The Langkilde lab has recently returned from its annual pilgrimage to the SICB (Society for Integrative and Comparative Biology) meeting, which this year was held in beautiful New Orleans! All our lab members presented talks, and had a great time networking, catching up on top research, and telling people about our own.
Below are some of our thoughts on the meeting, summaries of what we presented – and some tips for conference-goers from all fields!
“I talked about a paper I’ve been working on from our field season in Alabama last summer. Animals encounter environmental stressors daily; how does frequent, low-level stress influence survival and reproductive success? We show that, in Eastern fence lizards, a daily dose of low-concentration stress hormone led to increased adult mortality, and decreased hatching success of her eggs. This was the first conference I’ve been to where animal behaviour hasn’t been the primary focus – this reflects my broadening interests – I’m really excited by integrative research, so this meeting was a great way to see what other people are doing in more mechanistic fields (physiology, genetics, etc). It gave me lots of ideas for taking my own work forward!
My top conference tips are to contact people in advance that you want to talk to – that way you’ll be less likely to chicken out of approaching them! And – make use of Twitter before, during, and after the conference. It’s a great, informal networking tool. I met up with loads of top researchers that I’d first contacted on Twitter, and made lots of new friends!”
“I presented on the impact of a stress treatment on maternal behavior and offspring physiology and morphology. The thing I enjoyed the most was getting to meet not only senior researchers but also new researchers and hearing both of their perspectives.
My tip is to go to the socials and groups at night. They are fantastic places to talk with and meet people.”
“We already know fire ants are an invasive predator to many organisms, including fence lizards. What I want to focus on is the interaction of Fence Lizards and Fire ants, but as a prey source. This is the first step in my research, by using this study system, to understand how native species adapt to invasive species. The academic side of me really enjoyed meeting other scientist and just chitchatting in informal ways. The 24 year old side of me loved the location of SICB, considering it was in New Orleans!
Tips for conferences: Well this was my very first conference and I was worried about how to interact with so many bright and accomplished minds. The best and most cliché bit of advice I have, is simply be you. There is no point in putting on a different face, if you’re not even comfortable in it.”
“The water chemistry of vernal pools are often impacted by the environment. Changes in the pH and UVB impact the larval amphibians that live there. But how? Stay tuned for an upcoming publication! I LOVED meeting new people. I especially enjoyed meeting people who are working outside of my field of study. Their perspectives on my work are often very different than those within my field and I learn a lot from them.
My advice: TALK TO EVERYONE! You never know who you will meet. If you see a poster you don’t usually have an interest in, just stop and ask a question. If nothing else you may make a friend!”
“Going to SICB for the first time was fantastic, and New Orleans is a peculiar, very musical city, which I appreciated a lot. Being exposed to research from large variety of fields in biology certainly allowed me to appreciate other research areas better, so I definitely recommend attending talks that are out of your comfort zone. You never know what new ideas you might come up with!
Another valuable tip I have is, to never underestimate the power of a 25-minute nap during lunch break. The amount of information you receive over multiple days in a conference can be a bit overwhelming, so it’s important to rest whenever possible. It also helps you enjoy the nightlife better!”
Many of you would have played with Mexican Jumping Beans as a child. Ever wondered why it is that they jump? I presented some undergraduate-led research revealing what motivates this fascinating behavior.
Now that our field seasons are (mostly) over, the members of the Langkilde lab have been busy processing the blood samples we collected over the summer.
As I wrote last time, most of us are looking in some way at the impacts of environmental stressors on an animal’s behaviour, and the characteristics of the offspring they produce. In order to test these questions, we need to be able to quantifiably measure the stress levels of the animals we study.
To do this, we took blood samples from our study species in the field to measure levels of “stress hormones” (glucocorticoids, factors produced by the adrenal glands in response to stress). These hormones circulate in the blood, and correlate with the baseline stress levels of an individual – the more glucocorticoids we find in the blood, the more stressed an animal is. We determine the concentration of glucocorticoids in our blood samples by first centrifuging the sample to separate red blood cells from the plasma (the clear fluid in the eppendorf tube below), and then running the sample through an enzyme immunoassay.
Enzyme immunoassays work by using antibodies that bind to the factor of interest in a sample – in our case, the steroid hormone corticosterone. We add a known amount of plasma to each well of the plate (above right), and in each well, the corticosterone in the sample binds to the antibodies. The antibodies that aren’t bound by corticosterone are bound by a conjugate tracer, which gives off a colour. So, in the plate above, the more “yellow” the well appears, the less hormone it contains (meaning that more free antibody sites have been left to bind with the yellow tracer-bearing conjugate). We can compare the “yellowness” of each well with wells containing a known amount of hormone, and this allows us to calculate the concentration of hormone in each sample:
I’ve had a lot of fun learning these techniques this Fall, processing my lizard samples, and helping Chris process some of his rattlesnake samples! I’m looking forward to reporting back on the exciting results these data contribute to over the next few months.
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.
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.
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.
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!
When you tell people you are going to be studying lizards in Alabama for the summer, you get used to a raised eyebrow or two. The heat! The snakes! The bugs! When I told people I was going to be deliberately seeking out (ecological) public enemy number 1, fire ants, everyone made clear what I already knew – the theme of my summer was going to be STRESS.
In fact, stress (and in particular, maternal stress during gestation) is exactly what took me to Alabama. Stress during pregnancy can alter the characteristics of the resulting offspring, from morphology to behaviour. That’s assumed to be a bad thing. But could stress experienced by mothers during gestation actually program offspring for life in a stressful environment, giving them an advantage in the long run? This was the question I set out to test during my first, recently completed, field season.
For this study we focused on the eastern fence lizard, Sceloporus undulatus, a species well known to our lab. This lizard is particularly well suited to studying maternal stress because, as is the case for many reptile and amphibian species in the South East, it is subject to the considerable stress of coexisting with fire ants. We know a lot already about how fire ants change the behaviour and physiology of fence lizards – but what about the effects on the next generation through maternal stress effects?
A question this complex, with more than one generational level, required a number of steps. Step one was capturing gravid (carrying eggs) female fence lizards, which we did in May and early June. Having worked previously on mammals (meerkats) and birds (fairy wrens and hihi), this was a new and exciting experience for me! Safe to say, fence lizards (and herps in general!) quickly stole my heart.
Our next step was bringing the females into the lab, and subjecting them to a highly controlled “stress” treatment – a very low dose of a stress hormone every day, the equivalent of a single fire ant sting. It’s important to note that this is NOT a pain treatment – we use the hormone corticosterone, which is released as part of a lizard’s natural stress response, and which has a number of downstream effects including helping the body’s metabolic system turn amino acids into carbohydrates for use as fuel. In short, our treatment was tricking the lizards’ system (but not the lizard) into thinking they were in a stressful situation.
The next step was waiting for the females to lay their eggs, at which point our stress treatment ceased, and females were ready to be returned to the wild. We incubated their eggs (incubation takes around 50 days) and waited for the babies to hatch to begin the next step of our experiment…
We hypothesised that if maternal stress was adaptively programming offspring to be be better suited to a stressful environment (for example, by making them more responsive to predators, or better able to cope with frequent stressors), then we should see offspring from stressed mothers surviving better in stressful environments than offspring from mothers that did not experience stress during gestation.
To test this, we needed to create “stressful” and “non-stressful” environments in which to put the offspring. When we weren’t catching females or incubating eggs, we were building four 20x20m outdoor enclosures for this purpose! Thankfully, life in Alabama with fire ants everywhere is stressful enough, so we didn’t need to artificially create a stressful environment. To create a “non-stressful” environment, we removed fire ant mounds from two of the four enclosures. We hypothesised that in these enclosures, offspring from unstressed mothers should do best.
Once the offspring hatched, we put them into the enclosures and monitored their survival by checking them every day (not an easy task, they are small and wily!). I also recorded their habitat use, how far they were moving within the enclosures from their release spots, and how they responded to small, short-term stressors, like being picked up to be weighed. I’m now in the process of analysing this data, and am looking forward to seeing if our hypotheses hold true. Watch this space!
So, lizards aside, how did I cope with the stresses of a summer in Alabama? The heat – loved it! The snakes – try and keep me away from them! The bugs – who cares?! The people – a whole lot of new friends. There may be a million ways to die in the South, but there sure are a million and one things to love.
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.
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!
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.
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.
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?
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!
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!
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.
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.
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.
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…
There is a test we’d like to use in our fence lizards, called the phytohemagglutinin (PHA) skin test. It involves injecting the pad of a rear foot with a small amount of PHA, which stimulates part of the immune system, and then measuring the swelling that occurs. This swelling is small, and temporary, abating in a few days with no lasting damage. But the level of swelling can provide information about the lizards’ immune function.
Unfortunately, while this test has been used in humans, birds, rats, and even amphibians, it has not yet been validated in any reptile species. Ideally I would validate the test in our species of interest, the eastern fence lizard, but I needed a larger number of lizards than we can reasonably catch. So, instead, we decided to purchase some green anoles for this project.
In addition to seeing if the PHA test works in reptiles, we’re also trying to determine if the type of PHA used makes a difference, as there are many different formulations of PHA used, and each formulation may have a different effect. I’m also determining exactly what the immune reaction to the different PHA formulations are, and how this evolves over time after the injection.