The Lizard Log

The Langkilde Lab in Action


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What Makes Stress Stressful?

Stress is a familiar concept to most people. Paying the bills on time, entering a week of exams, caring for a sick loved one, or even sitting in heavy traffic on the way to work. When you get stressed out, your body goes through a series of changes to help you deal with that stress. This stress response includes both physiological and behavioral changes and is generally a good thing! For animals, the physiological stress response can mobilize energy and trigger important behavior, perhaps to get away from a predator. It can also enhance immune function in the short term to prepare for wounding or infection that might occur as a result of that stressful encounter.  Short term stress is typically called “acute,” and the resulting stress response is very similar across vertebrates—because it works!

Stressors come in a variety of forms.

Stressors come in a variety of forms.

If stress lasts for a long time, however, there can be costs to using so much energy on the stress response. If you have ever become sick after a week of exams or a particularly challenging week at work, you know what I’m talking about. Long term stress—typically called “chronic” stress—can suppress immune function as well as growth and reproduction.

Sometimes, however, these generalizations don’t hold up—short term acute stress may produce negative consequences or long term chronic stress may produce positive outcomes. This got us wondering—just what is it about stress that might lead to negative consequences? We discuss just that in our latest paper published in General & Comparative Endocrinology, which is now available online.

Now published in GCE!

Results published in GCE.

Stress is typically defined by duration—as acute or chronic— in the scientific literature as well as in veterinary and medical practices. I wanted to investigate not only stressor duration, but also other characteristics of the stressor, like frequency and intensity. There is some evidence that frequency and intensity affect the outcomes of stress, but few studies have attempted to look at how they might interact with each other or duration.

To test these ideas, I exposed fence lizards to different stress regimes. I did not want to use a physical stressor, so we instead manipulated a stress relevant hormone. When the stress response is activated, the glucocorticoid hormone cortisol (in humans) or corticosterone (in lizards) is secreted by the adrenal glands. We often measure CORT as a proxy for stress, and we can give a lizard CORT to replicate the increase in CORT that occurs in response to a stressor. After dissolving CORT in oil, one simply drops the solution onto the back of a lizard and it is quickly absorbed. One can also put the CORT-oil solution into a hormone patch for a slower release. These work a lot like a nicotine patch in humans, just with CORT and on a lizard.

A fence lizard with a slow release CORT patch.

A fence lizard with a slow release CORT patch. Stylish!

We used different regimes of CORT application to help determine how duration, frequency, and intensity affect immune outcomes in lizards. After the 9 days, we measured the innate immune system in two ways [similiar to  this post], both of which roughly measure the ability of lizard blood to deal with foreign particles. One of these assess hemagglutination, which is the ability of plasma to hold sheep red blood cells in suspension. Higher scores indicate greater ability, or better immune function.

The completed hemagglutination assay.

A completed hemagglutination assay.

Some of our results were particularly interesting:

Two of our treatments would be considered “acute.”  Both were short in duration and differed only in the intensity of the dosage. Exposure to short duration low-doses of CORT  enhanced immune function (hemagglutination), while exposure to short duration high-doses suppressed immune function. This indicates that intensity is an an important factor when considering immune outcomes of stress.  This matches up with what we know about PTSD—short but intense stressors can have lasting effects in that context as well.

Additionally, while both of these treatments mimic “acute” stress, they produced opposite results. This demonstrates that the terms “acute” and “chronic” may not be enough to sufficiently characterize stress. These terms are also inconsistently used in the scientific literature, which only adds to the confusion.

Three of our treatments received the same average amount and total amount of CORT over each three day period and over the duration of the experiment but differed in how they were distributed–they varied in duration, intensity, and frequency. All three of these treatments, however, produced different outcomes—one enhanced immune function (frequent low doses), one suppressed immune function (infrequent high doses), and one was somewhere in the middle (slow release of the high dose). This suggests that average or total amount of stress (CORT) may not be comprehensive enough to characterize how the stress is experienced or accurately reflect its outcomes.

Although frequency and duration had lesser roles in this experiment, intensity was a major factor in altering the immune consequences of stress. We recommend that researchers consider and report aspects of stress other than duration, such as intensity and frequency, to aid our understanding of the consequences of stress. We should also move away from the terms “acute” and “chronic,” as they are inconsistency used and incompletely describe stress.

Because the environment is changing due to climate and human activities, wild animals will be exposed to new stressors or familiar ones more often. Determining what about stress leads to negative consequences is important to understand how species will respond to environmental change.

How will wild organisms respond to the stress of environmental change?

How will wild organisms respond to the stress of environmental change?

These results are published in General and Comparative Endocrinology. This research is also featured on the Penn State CIDD website, here.

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Do fence lizards take a chance and eat stinging ants when exotics advance? Indeed they do!

Part 2 of 2 in the fence lizard fire ant saga: Rapid evolution of fence lizards (Sceloporus undulatus) in response to selective pressures imposed by red imported fire ants (Solenopsis invicta).

I’m a postdoctoral research fellow in the Langkilde Lab who studies the ecological mechanisms that result in evolution. My interests range from the evolution of life histories in response to climate change to behavioral evolution in response to invasive species to the evolutionary significance of culture.  Most of my research, however, is on Sceloporus lizards (AKA Spiny lizards or Swifts), focusing on their genetic and plastic responses to environmental change and the underlying interactions between physiological (e.g. hormonal), behavioral (e.g. resource use and niche construction), and epigenetic mechanisms. My research endeavors have brought me to Costa Rica, Panama, Mexico, the subtropics of Florida, and inside Biosphere 2 in the Arizona desert, but I am currently focusing on lizard evolution in the southeastern US, which brings us to the current continued blog post.

So, in the first chapter of the Saga we found out that fence lizards are adapting to habitats where they coexist with fire ants, which quickly find and attack lizards when on the ground. Some fence lizards dance and run away from fire ants when attacked, and the number of lizards that exhibit this behavior increases the longer a population has experienced fire ants. See the first chapter of the Saga here.

Fire ants attacking lizards is interesting, but what is even more interesting is that this interaction can be turned on its head!  Ants are a normal part of a fence lizard’s diet, so why wouldn’t fire ants be susceptible to being eaten by a fence lizard? Fire ants are susceptible! We’ve noticed while in the field that fence lizards do occasionally eat fire ants during encounters.  Not surprising, until you pick up a little insider information about a strange twist.  One of Tracy Langkilde’s studies revealed that eating fire ants can decrease lizard survival!

If it is bad for lizards to eat fire ants, why do they do it?  In light of what appears to be evolution with regard to the dance and run behaviors, we hypothesized that fire ant-eating behavior of fence lizards should be less frequent in populations that have experienced fire ants for a longer time (i.e. more generations). We tested this by recording fire ant consumption during staged encounters between fire ants and fence lizards from both fire ant invaded (experienced) and uninvaded (naïve) lizard populations. We also tested both juveniles and adults because we knew that they have a tendency to respond to fire ants differently.

We found a complex relationship that somehow supports both what we already knew from previous experiments (adults in fence lizard populations are adapting to the presence of fire ants) and our newer hypotheses about juvenile lizards adapting to the fact that eating fire ants can be toxic!  It seems that adult fence lizards from populations that have been coexisting with fire ants for a long time eat fire ants much MORE frequently than lizards that have never experienced fire ants.  What!?

AntInsideMouth - T. Langkilde, T.R. Robbins

Photo credit: T. Langkilde, T.R. Robbins

Figure 2 - Robbins Langkilde 2012 - JEB

Fire ant consumption by lizards. The proportion of field-caught (a) and laboratory-reared (b) adult (open squares) and juvenile (solid squares) fence lizards, Sceloporus undulatus, from a fire ant-invaded and uninvaded site that consumed fire ants during fire ant attack. Points represent mean values ± 1 standard error.
Figure – Robbins and Langkilde 2012 J Evol Biol 25(10):1937-46

We also found, as we hypothesized, that juvenile fence lizards from populations that have been coexisting with fire ants for a long time eat fire ants much LESS frequently than their inexperienced counterparts.  So we see changes in feeding behavior in fence lizards after fire ants invade their habitat, just like we saw with the dance and run anti-predator behaviors. What is more fascinating, however, is that our results with regard to feeding behavior suggest what is called an ontogenetic shift in selection pressures.  That is, it is more adaptive to behave one way while young and then behave the opposite way when older!  Fire ant invaded habitats select (via natural selection) juveniles that do not eat fire ants, but can learn to eat fire ants once they grow up!

Next, obviously, we wanted to test if and how well juvenile lizards learn to eat fire ants.  Our hypothesis for this experiment was actually that the lizards would learn NOT to eat fire ants because they get stung in the mouth when they eat them. At some time during their life with fire ants they seem to learn to eat fire ants, but we thought it would be after they were adults because fewer juveniles from the invaded site had eaten fire ants when on the mound and under attack (see above).

lizfirenear

Photo credit: T. Langkilde, T.R. Robbins

We were wrong!  When it comes to eating fire ants, the longer lizards are exposed to fire ants the more lizards eat them!

Figure 2 - Robbins et al 2013 - Biol Inv

Proportion of lizards from invaded (open circles and broken line) and uninvaded (solid circles and solid line) populations that ate a fire ant over a 6-day period. During this period lizards were fed 1 fire ant followed later by 2 crickets each day, representing a subsistence diet. Points show proportions ± 1 standard error.
Figure – Robbins et al 2012 Biol Inv 15: 407-415

We even found that more juvenile lizards from the invaded site ate fire ants during the experiment than those from the uninvaded site (lizards naïve to fire ants).  So, juvenile lizards appear to learn to eat stinging ants pretty quickly when they are not on a mound being attacked!  It changed from 50% to 80% of lizards eating fire ants within 6 days.  Maybe fire ants are addictive like hot sauce is for us! Endorphins can be powerful rewards.

I know, it’s a little confusing.  Juveniles from invaded sites (i.e. that have experience with fire ants) eat fire ants less often when on the mound being attacked (first graph), but more often when fed one ant each day over a 6 day period (second graph)?  Well, the two scenarios are a little different with a lizard being under attack by many fire ants in the first and in the other only being exposed to one lonely fire ant.  And that may have something to do with the it.

The effects of envenomation are mass dependent, so the fact that juvenile lizards are small means that they can be overcome by fire ant venom faster than adults. When a juvenile lizard is on a fire ant mound and notices many potentially stinging ants, it doesn’t think to eat them as much as it thinks to dance and run away.  However, away from fire ant mounds fire ants are often an abundant potential food source.  When fire ants invade habitats they pretty much take over and push out many of the other arthropods that otherwise serve as food for lizards.  Although eating fire ants can increase the chances of a lizard’s early demise, eating a few fire ants here and there will not overtly harm all juvenile lizards.  Even in the study that found an increase in mortality after eating fire ants there was still a 66% survival rate.  So, because venom effects are mass dependent, it’s possible that juvenile lizards that survive and grow up (and thus get bigger) can eat more fire ants (and get stung) without feeling the negative effects of fire ant venom.

Although natural selection appears to select juvenile lizards that do not eat fire ants when being attacked, it seems they like to get stung in the tongue as they become less young!  But this tale has yet to be completely sung! We only fed the lizards 1 fire ant per day, which may not be enough to make them learn to avoid eating them.  They may easily forget what they had for breakfast yesterday and thus need to experience eating and getting stung on the tongue a few times a day to learn to avoid eating fire ants.  Or not.  We are analyzing experiments we designed to test just that right now!

So the saga continues . . .


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Signs From Above

One of the great things about our research is that it takes us to a great variety of places in search of lizards. Whether in Arkansas, Alabama, or New Jersey, we see the interesting parts of America. Or, if nothing else, at least how it’s advertised. So, as a new year approaches, we decided to offer the following recap of some of our less-scientific, but nonetheless interesting observations from the field.

EmuSign

Is this a thing?

elephant

The permanent resident across the street from our usual hotel in TN.

marbles

For distinguished visitors to a park in TN.

froglegs

mmm mmm good.

jewelry fudge knives

I’ll take two, please.

ServiceCenterSign

A fine establishment, if ever I saw one.

measles bridge

In TN. I hope he’s not catching.

murder-creek

It’s the place to be.


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If lizards had pants the pants would have ants and the lizards would dance. Indeed they do!

Part 1 of 2 in the fence lizard fire ant saga: Rapid evolution of fence lizards (Sceloporus undulatus) in response to selective pressures imposed by red imported fire ants (Solenopsis invicta).

Dr. Travis R. Robbins is a postdoctoral research fellow in the Langkilde Lab who studies the ecological mechanisms that result in evolution. His interests range from the evolution of life histories in response to climate change to behavioral evolution in response to invasive species to the evolutionary significance of culture.  Most of his research, however, is on Sceloporus lizards (AKA Spiny lizards or Swifts), focusing on their genetic and plastic responses to environmental change and the underlying interactions between physiological (e.g. hormonal), behavioral (e.g. resource use and niche construction), and epigenetic mechanisms. His research endeavors have brought him to Costa Rica, Panama, Mexico, the subtropics of Florida, and inside Biosphere 2 in the Arizona desert, but he is currently focusing on lizard evolution in the Southeastern US, which brings us to the current blog post.

Dude

Photo credit: T.R. Robbins

For the past three years I have been studying how fence lizards change their behavior and morphology after red imported fire ants invade the fence lizard habitat. This amazing study system that Dr. Tracy Langkilde fostered almost a decade ago reveals more exciting ecology with every research project!  Tracy found an interesting trend across fence lizard populations that were invaded by fire ants at varying times in the past.  The longer fence lizard populations coexist with fire ants, the more fence lizards in each population begin to respond to agonistic encounters with fire ants.

Change in use of (a, d) body twitch (solid symbols) and (b, e) flee (solid symbols) defensive behavior, and (c, f ) the relative hind limb length (shown as hind limb length/snout–vent length, SVL); of adult vs. juvenile fence lizards (Sceloporus undulatus) across sites with different histories of fire ant invasion. Open symbols represent behavior exhibited during control trials conducted in the absence of fire ants. Sexes are pooled for all panels. In all panels, values for adults represent mean 6 SE for 20 male and 20 female lizards from each site; values for juveniles represent mean 6 SE for 157 juveniles born to 16 females from Site 1, and 128 juveniles born to 18 females from Site 4. Figure  – Langkilde 2009 Ecology 90(1): 208-217

Change in use of (a, d) body twitch (solid symbols) and (b, e) flee (solid symbols) defensive behavior, and (c, f ) the relative hind limb length (shown as hind limb length/snout–vent length, SVL); of adult vs. juvenile fence lizards (Sceloporus undulatus) across sites with different histories of fire ant invasion. Open symbols represent behavior exhibited during control trials conducted in the absence of fire ants. Sexes are pooled for all panels. In all panels, values for adults represent mean 6 SE for 20 male and 20 female lizards from each site; values for juveniles represent mean 6 SE for 157 juveniles born to 16 females from Site 1, and 128 juveniles born to 18 females from Site 4.
Figure – Langkilde 2009 Ecology 90(1): 208-217

Usually this lizard species uses crypsis to avoid predation, so it is not prone to moving when something, that is usually harmless (i.e. not a fire ant), crawls over it. The lizards respond to fire ants, however, by dancing (twitching) and running away! And they evolve longer hind limbs so they can be really efficient at it!

Most of our data collection has been about how fence lizards respond to fire ants when they find themselves being attacked on top of a fire ant mound.  Fire ants are quite aggressive when they find someone knocking on their door. Unfortunately, especially for those of you that live with fire ants in your yard, fire ants spend a lot of time away from the mound ubiquitously foraging and roaming around the habitats they invade. Lizards surely encounter fire ants when they have the displeasure of accidentally knocking, but most of the time lizards are basking in the sun or foraging for food somewhere other than fire ant mounds. Thus, we wondered how often a fence lizard would encounter a fire ant away from a fire ant mound, so we conducted an experiment.  We placed lizards 4 meters away from a fire ant mound (and fire ant mounds are approximately 10 meters apart where abundant, so this almost as far as you can get from one!) and observed them to measure how long it would take for a fire ant to find the lizard.  We also measured the behavioral response of the lizard and its effectiveness in avoiding an attack.

Fence lizards were found by fire ants within 105 seconds on average!

We call the first fire ant to find a lizard a “scout”, and this single ant is not much of a threat to a fence lizard.  However, that scout tells his buddies where to find the lizard, and a bunch of ants start heading toward the lizard to attack.  We call this “recruitment”, and this higher number of ants attacking is potentially dangerous.  It only takes 12 ants to immobilize an adult fence lizard in 60 seconds.  But, don’t worry, we never let this happen during our trials. We hypothesized that fence lizards that grew up with fire ants would enact their dance and run technique (twitch and flee behavior) whereas naïve fence lizards would not.  We also hypothesized that the dance and run would be effective at curtailing the recruitment.  If fence lizards responded to the scout before the scout could bring back recruits, the recruits would come to an empty spot, and the lizard in its new spot would no longer be threatened by an attack.

Our results suggested that this was indeed the case!  Experienced lizards (those caught in the field at the invaded site) danced and ran when they encountered the scout.

Figure 1 - Freidenfelds et al 2012 - Behav Ecol

The proportion of field-caught (gray bars; n = 40 from each site) and laboratory-raised (white bars; n = 22 from each site) adult fence lizards from an invaded and uninvaded site that behaviorally responded to attack by red imported fire ants on a fire ant mound. Bars represent mean values ± 1 SE. Different letters above the bars denote significantly different groups.
Figures – Freidenfelds et al 2012 Behav Ecol 23: 659-664

We found that experience with fire ants (lizards from the invaded site) affected only adults, however, because juvenile lizards from all populations were scaredy-cats, running away quickly. We also found that dancing and running in response to a scout was an effective strategy to escape the danger of an attack by recruits.

Figure 2 - Freidenfelds et al 2012 - Behav Ecol

The proportion of fence lizards that had red imported fire antsrecruit to attack them after being located by a fire ant scout, comparing responder (lizards that behaviorally responded to fire ants, n = 13) and nonresponder (lizards that did not respond to fire ants, n = 7) adults. Bars represent mean values 6 1 SE. Different letters above the bars denote significantly different groups.

Our results suggest that when lizards grow up with fire ants they change their behavior in an adaptive way that likely increases their biological fitness by avoiding attacks by stinging fire ants (likely keeping them alive and in better moods). Overall, we have found that the longer a population has coexisted with fire ants, the more fence lizards in the population exhibit the changes, suggesting that these behaviors and morphologies are evolving to help fence lizards adapt to deal with the pesky, painful, and potentially portentous fire ants.  We are currently examining whether or not these behaviors are inherited by comparing behaviors of mothers to their offspring once they become adults.

Stay tuned . . .


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Redemption in the Deep South

This undergraduate guest blog post has been dispatched by Mark Herr, a junior from Los Angeles who is majoring in Wildlife and Fisheries Science at Penn State. Mark is a member of the Penn State Presidential Leadership Academy, and is interested in continuing on to graduate school to study behavior, ecology, and, of course, reptiles & amphibians:

This past spring I applied for, and with the help of Dr. Langkilde received, a Penn State Discovery Summer Grant to conduct independent research. Initially, I planned to conduct two projects on similar systems. Unfortunately, only the second project (hence the title of this post) resulted in a successful field season. Which isn’t to say that the first project wasn’t valuable – it was perhaps the most valuable research experience I’ve had yet – but its value really lay in lessons learned rather than any publishable results!

Before I explain the project, I want to first give a shout-out to Drs. Langkilde and Sean Graham. Dr. Langkilde managed to let me know that my initially proposed projects were all rather grandiose and unfeasible, while convincing me to keep on firing away with ideas. Eventually, I sent her an idea that we both agreed was novel, and more importantly, possible. Sean went out in the field with me during every day of sampling and made the project possible. This is all the more impressive because he is a post-doc researcher and I am just an undergraduate – which says much both about him and the atmosphere that Dr. Langkilde fosters in her lab.

Dr. Sean Graham does his best to become an internet sensation by displaying a cottonmouth using the standard forced perspective method so that it appears to be of monstrous size. However, this snake is actually only a little over 3 ft. long. The camera really does add a few pounds.

Dr. Sean Graham does his best to become an internet sensation by holding a cottonmouth safely out of striking range while using the standard forced perspective method so that it appears to be of monstrous size. However, this snake is actually only a little over 3 ft. long. The camera really does add a few pounds.

I don’t want to delve into the specifics of my project idea in California, both because it will bring back the stinging memory of defeat (just joking!) and poison oak rashes so bad that they probably warranted hospital visits – both for Sean and I! Luckily, Sean and Dr. Langkilde had foreseen the fact that all might not go as planned with one of the projects – and so they had suggested that we conduct a second project as insurance. And so it was this “insurance policy” that became my last true hope for some publishable research during the summer break.

My project ran side by side with other work being conducted in Alabama by the Langkilde Lab, which allowed me to help out with other projects when I wasn’t out in the field with Sean collecting snake blood. Yes. Snake blood, and no, this didn’t involve door-to-door salesmen selling cure-alls or primitive rituals by witch doctors.

Sean and I investigated how the stress hormone (corticosterone) concentrations in Cottonmouths (Agkistrodon piscivorus) were related to their anti-predator behavior. Cottonmouths are large bodied, aquatic pit vipers native to the southeastern US. Most importantly, they are abundant. The snakes were honestly even more abundant than I had expected – even though we did have a period where we had trouble finding any, but more on that later.

They are also famous for being aggressive, or, at least that is what the man on the street will say – the consensus among scientists and in peer-reviewed research is that they aren’t anything close to the bloodthirsty mankillers they are made out to be. Cottonmouths do, however, have an extensive suite of anti-predator behaviors. They vibrate their tails (even though they have no rattle), they hiss, they can strike, and they can open their mouth wide in what is called a ‘gape’ in order to convince a possible predator that they aren’t worth the trouble. Actually, this gaping behavior is what gives them their common name – the inside of their mouths has a white lining that is highly visible (especially in their often dark habitats).

A Cottonmouth from the Everglades showing the display for which it is named.

A Cottonmouth from the Everglades showing the display for which it is named.

The fact that this species has so many different anti-predator behaviors means that I was able to formulate a point system that would rank each individual snake based on how “defensive” it was acting. The procedure was to approach the snake and stand in close (but safe) proximity to it for 15 seconds and then grasp it mid-body with a set of snake tongs for another 15 seconds – all the while taking note of every behavior that the snake exhibited. We would then use a snake tube to restrain the animal and take a blood sample.

As I write this I am laughing out loud at how simple that last sentence makes the blood drawing seem.

The problem, as you might imagine, is that often times (read: every time) the already defensive snake wants nothing more than to avoid slithering up a tight clear plastic tube so that we might get our blood sample safely. For obvious safety reasons, the entire tubing maneuver has to be completed using nothing but a set of snake tongs and a tremendous amount of patience – tubing is the safest way to handle venomous snakes – by far (both for the snakes and the researcher). It’s the industry standard technique.

The process goes something like this:

  1. Using a pair of snake tongs, the snake is grasped firmly enough at the midbody to prevent the snake from escaping but not so tightly as to injure the animal.
  2. The tube is maneuvered such that it fits over the snake’s head, and ideally the snake will crawl up the tube such that its body is half inside and half outside the tube, with the snake’s posterior body portion and tail hanging out of the end.
  3. Swiftly and steadily, the snake is grasped at midbody at the exact point where it hangs out of the tube – with the hand holding the snake firmly grasping both the animal itself and the tube to prevent the snake from either moving further forward or backing out.

Step #2 is sometimes easy, as the snake will cooperate and crawl up the tube as soon as it is able. Usually, though, it is not so easy. More often it would rather keep dodging and moving its head away. Even more often it would rather just strike the tube repeatedly. This process was further complicated by the fact that we were on a tight time schedule –we needed to obtain blood from the snake before its hormone levels had risen significantly (which takes only a few minutes). Did I mention the fact that we were unable to physically touch the snakes until they were in the tube?

A safely and successfully tubed Cottonmouth on display after obtaining a blood sample.

A safely and successfully tubed Cottonmouth on display after obtaining a blood sample.

We went out during the day and at night searching for snakes, usually spending at least 4-5 hours at a stretch slogging through swamps in waist deep swamp water, and we managed to get to within about 5 snakes of our sample size when we hit a wall. No. More. Snakes.  I can’t even remember how many times Sean and I ventured forth without finding even a single snake. It was as though cottonmouths had gone from being the most common snake in the Conecuh National Forest to almost nonexistent. A change in the weather may have been the culprit, but I wasn’t nearly as concerned with the source of the problem as with the prospect that I might not find enough snakes to complete the research.

Luckily, we had a solution. Sean had a location that he knew would guarantee snakes en masse – unfortunately, it was too far away for just a day trip. Our solution was to hit this magical spot on the way back to Pennsylvania on our very last day.

I can’t tell you how nervous I was when we went out that final night.

To set the stage:

  1. We didn’t have enough snakes. More importantly, we really needed to find a specific subset of snakes, adult males, which are significantly more difficult to locate than adult females or juveniles.
  2. We absolutely had to leave for Penn State the next morning, making this the absolute last possible time to get enough snakes to complete the project.
  3. The previous four days hadn’t yielded even a single snake.
  4. Just for dramatic effect, there was an absolutely MASSIVE electrical storm just prior to our sojourn, shaking the ground and lighting up the sky like a child repeatedly turning the lights on and off inside an otherwise pitch black room.

Well, that night could have shared a title with this post: Redemption in the Deep South. After working from 8:00 pm to 2:00 am, slogging through waist deep (read: sometimes neck deep) blackwater while exhausting our drinkable water, getting lost, and receiving (conservatively, of course) 1,000,000 mosquito bites, we found our 5 snakes. Three of the five were adult males. Our goals were complete. Victory.

I am still in the process of inputting data and running samples, so I can’t yet tell you how stress hormone levels in cottonmouths relate to their behavior. What I can tell you is that working through the trials and tribulations of this summer’s research has made me a better scientist by far. I have many to thank for making this experience possible, but my highest gratitude extends to Tracy Langkilde, Sean Graham, and the cottonmouths of south Alabama. Thanks guys.

Adapted from Mark Herr’s Presidential Leadership Academy Blog


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Hanging-thieves!

No, it’s not the name of a cool new band you haven’t discovered yet; the Hanging-thieves are a genus (Diogmites) of robber flies that is known for hanging by one or two legs from a perch site while consuming their prey. Robber flies (family Asilidae) are also known as assassin flies, because they catch other bugs while on the wing and eat them with their piercing mouthparts. In general, robber flies are considered to be beneficial, as they eat many pest insects.

A hanging-thief chows down on a freshly caught wasp .

A hanging-thief chows down on a freshly caught wasp .

I was lucky enough to stumble upon a Hanging-thief (it looks like Diogmites salutans) as it was engrossed in eating a wasp. The robber fly was perched on one of my AED’s (Armadillo Excluder Devices), small wire cages that I set up to protect my fake lizard nests from predation by wily armadillos (that story another time…). The fly had already paralyzed its prey with venom, which also contains enzymes which liquefy the prey’s innards (as in spiders). As I watched, the robber fly carefully manipulated the wasp, turning its body over and around, and inserting its proboscis into likely sites, as if its prey were some sort of delicious juice box. In the video below, you can see the mouthparts of the fly working to slurp up its presumably delicious meal.

My favorite part of seeing this robberfly was observing its moustache, or mystax, which is so tough that it may help protect the fly from injury when it is subduing struggling prey.

Who wore it better: Diogmites or Ron Swanson?

The mystax is among the most fearsome of moustaches in the animal kingdom.


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Fire Ants Love Bacon

As Gail mentioned in a previous post, one avenue of our lab’s research involves looking at the behavioral responses of fence lizards to fire ants. These behaviors include leg twitches, tail writhing, full body jumps and shakes, head wipes, and eating attacking fire ants. We also are currently investigating how these responses vary with context; to whit, we want to know whether fence lizards respond differently to fire ants based on whether those ants are defending their mound or if the ants are out foraging for food.

Fire ants, like many ant species, will construct foraging trails to a food source once it is discovered (as seen below).

Scout ants, upon encountering a food item, will lay down a pheromone trail that other ants will follow to allow them to feed and return with sustenance to the mound. To effectively study how lizards respond to ants in “foraging mode,” we need to generate lots of foraging trails of ants. And with ants, as with college students, if you want them to show up, you need to bribe them with food.

Previously, we’ve used both peanut butter (creamy…fire ants hate chunks) and hot dogs as fire ant bait.

HotDogBait

Fire ants chow down on a delectable bit of American cuisine.

Fire ants, like humans, are attracted to foods with lots of fat and protein (especially when they are brooding). This week, however, I stumbled upon an even more tempting proposition for the ants: good old bacon. At breakfast, I tucked a half-finished piece of bacon into my pocket, and scattered several chunks of it in the sandy area that we use for our foraging ant trials. Within 15 minutes, the bacon was swarming with fire ants, attracted to the high level of deliciousness of the baits. A visit from a hymenopteran in a yellow jacket brought a touch of class to the party (see below).

While we won’t be using bacon everyday to seed our foraging trails, we have definitively learned that fire ants share the human propensity for unhealthy but scrumptious foods.