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.
This past week, the Langkilde Lab worked to complete one of our Christmas traditions: decorating our lab door for the Biology Department’s Holiday Door Decorating Contest. As two year running champions, we know what it takes to win the contest: a great idea, skilled execution, and a whole LOT of time. This year, we’re pretty busy and didn’t want to invest ludicrous amounts of time into a project that, while peer-reviewed (via web-based surveys…) won’t contribute much to the lab’s impact factor. So, after seeing some sweet Star Wars themed snowflakes during a brainstorming session at lab meeting, we decided to make Herpflakes! Gail worked her Powerpoint magic to turn run-of-the mill clip art into geometrical fun. With her high-powered scissors, we made snowflakes representing the different study organisms used in our lab: lizards, frogs, snakes (we don’t really study them, we just like them), and ants.
After cutting out our various flakes, we decided to add a snake catching them on his tongue at the bottom of the door. A quick Santa hat using repurposed fur from previous years’ doors completed the look!
With the door made, there was only one task left: to pick a title! We tossed around numerous ideas over the period of a couple of days, and even considered naming it “These Snowflakes are Animals” when we wondered if viewers would be able to recognize the different animals in a picture. But, we finally settled of “Let it Ssssnow,” an incredibly sophisticated pun.
Below I’ve listed the potential titles pulled from the brainstorm board in our conference room so you can see just how hard up we really were. If you have a great alternate title that we didn’t think of (or prefer one of our other options), put it in a comment!
Slitherin’ in a Winter Wonderland
Have a Merry Hissmas
Let it Ssssnow
These Snowflakes are Animals
Deck the Halls with Animal Snowflakes
Give the Gift of Herps
Have a Snakey Flakey Hissmas
Over the past several years, I like to think I’ve been a sort-of successful spy on the secret lives of herps. As a behavioral ecologist with a focus on reproductive behavior, invading animal privacy comes as part of the job. Thankfully for my conscience, my subjects don’t seem to mind… or really even notice. One of the plus sides of working on reproductive behavior is that— at least when sex is in the offing—animal subjects seem to care a lot less that big, lumbering, non-predatory researchers are nearby. In this post, I’d like to share with you the delightfully graphic details of one of my spying expeditions on eastern fence lizard (Sceloporus undulatus) sexual competition.
Males of all species tend to fight. A lot. Not exactly a ground-breaking revelation. (Females fight too, but generalizing over all species… let’s face it: males on average tend to fight more.) What is immediately apparent across the animal kingdom is that fighting with males of your same species can be very, very costly. Think about some examples of “classic” male weaponry – antlers, teeth, tusks, horns – they’ve evolved to wound, maim, injure, and even kill.
Fence lizard males—despite their modest size, lack of obvious weaponry, and generally sweet nature (a spy’s personal opinion)—also can be absurdly aggressive when it comes to sex. Quick natural history lesson: Male fence lizards defend home ranges that abut or overlap those of other males; females have smaller home ranges that are nestled inside one or more male home ranges. When males fight with each other, it’s often over access to females who, from the males’ perspective, wander too much. Females watch males fighting and may make their own mate choice decisions based on what they see. So, you might imagine that it would behoove males to give each fight their all, not only to win the right to the lady, but also to impress her. However, that’s not what we’ve observed. Instead, we see a wide variation in fighting strategies: some male lizards are downright timid, backing down pretty quickly, while others go right for the throat, so to speak.
Above: A bout of territorial competition between two Sceloporus (either graciosus or occidentalis) involving chases and whole-body shudders.
As part of our research, we staged encounters between males to figure out why so much variation exists in how and when males escalate fights. We placed males in a laboratory arena, separated from each other (and a tempting, lovely, lady lizard) by clear glass to prevent any real bloodshed between competing males. Instead of observing who the winners and losers of real, pitched lizard battles were, we used an excellent indicator of contest escalation—display behavior. Display behaviors are body postures and movements that convey messages to competitors, for instance, lizard “pushups” and whole-body shuddering that are signals of territory assertion. Using video recordings, we carefully documented every display behavior each male sent to his competitor—essentially transcribing a non-verbal dialogue between two increasingly angry males. We were able to “decode” this dialogue, assisted by information collected and previously published by other researchers around the world. And what we found after decoding these secret messages was pretty surprising.
Because fighting can be so costly (not only is fighting exhausting, but there’s a high risk of getting a serious bite), we initially guessed that differences in the tendency to escalate fights may exist because males that can afford to lose more (“big and strong” males) were more willing to take the chance of having a costly encounter than scrawnier males. What we observed, however, was almost the exact opposite. Of the two males in each trial, we found that the wimpier of the two consistently responded to his competitor’s display behavior with more aggressive behaviors. The really cool part about this is that the tendency to respond with aggression isn’t hardwired— it’s not that small males were always more aggressive, but instead that the males that were smaller than their competitors were more aggressive. A nuanced, but important, distinction. Put a medium sized male with a bigger competitor, and he’d act like a tough guy; put the same lizard with a tiny competitor, and he wouldn’t bother to give the challenger the time of day. So, it seems like fence lizard males are somehow assessing their own chances of success in a fight against every individual competitor that they face, and adjusting their strategies accordingly. Being willing to escalate a fight may be crazy risky, but also could literally be the only way to defeat a physically formidable opponent. Littler guys need to be willing to take the risk in order to reproduce. Bigger males are more chill: there may be no need to waste time and energy doing displays when they don’t need to, since they’ve really got the size advantage if the confrontation were to come to blows (or bites!).
In the last of our undergraduate blog posts for this semester, we’ll hear from Tommy Cerri, a sophomore in the Langkilde Lab. Tommy is majoring in biology- vertebrate physiology option with an intended minor in psychology. In the community he is a member of the Morale committee for THON, a part of Global Medical Brigades, and also a member of Pre-Med Society. After college he plans on attending medical school and becoming an emergency room attendant. His post is below:
Last semester, in the spring of my freshman year, I applied for and received a grant to work in the Langkilde Lab from the NASA freshman undergraduate research program (FURP). Since then, my time in the lab has been split between recording data for Travis Robbins, a post-doc in the lab, feeding the animals, and assisting with collecting data on tadpoles for Brad Carlson, a graduate student in the lab. As I’m only in the midst of my second semester in the lab, I haven’t had the time to begin my own research project yet. I currently am gaining experience and understanding, so that in the near future, I’ll be able to take on such an independent project.
During my first semester in the lab, I began with entering and managing data regarding juvenile lizard reactions to fire ants under various stresses. I worked to compile this data into one spreadsheet to be easily analyzed for Travis’s study on these lizards. I also fed the lizards weekly. Feeding the lizards was always a task because, ironically given that I am a biology major, I am frightened by them. I had to fill up their water bowls and after this give each lizard a few crickets; I am actually even more frightened of crickets! I got the hang of the feeding in the first few weeks, and Travis even showed me how to handle lizards! All my progress came crashing down one afternoon, though, when I was dropping some crickets to one angry lizard. Suddenly, he jumped up (about six inches) onto my arm and then jumped one more time out of the cage. I was frozen in absolute fear. A more experienced undergrad was nearby to quickly scoop up the pesky thing and return him to his tub. However, I was scarred forever from the experience, and I can no longer see lizards in the same way again.
This current semester, I have been working with Brad on photographing groups of tadpoles. Brad’s research primarily focuses on the variability of tadpole phenotypes induced by the environment. We know that animals can vary among one another within populations, but what Brad is trying to uncover is what factors impact how much of this variability there is. He raised groups of tadpoles in wading pools and subjected them to three different treatments. The first treatment was the presence of a predator or lack thereof. The second was either a large density of tadpoles within a pool or a small amount of tadpoles. The last treatment was whether food was distributed evenly or unevenly to different areas of the pool in which the tadpoles are held.
My role in the experiment comes with the collection of data. I am responsible for weighing all the tadpoles from each pool as well as photographing a randomly selected 15 tadpoles from each group. The selected photographed 15 tadpoles will then be viewed to measure the length and depth of the tail of each individual (described in Andrew Watt’s post). The resulting data will then be analyzed to determine the amount of morphological variability that occurs within the same population of tadpoles from the differing environmental treatments.
The results of the data have not yet been analyzed to determine how the experiment turns out. Up to now I have had a great experience working with scientific tools and really getting hands-on experience with research here at the university. It has been an eye-opening experience up to now seeing what really goes on before papers of findings are published and how much work really goes into it! Next semester I am taking an ecology and ecosystems class and am very interested to see how what I have experienced in the lab ties in with what else I will learn. I still have so much to learn and am very excited to improve my knowledge of biology and contribution within the lab.
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.
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.
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.
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.
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.
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 . . .