The Lizard Log

The Langkilde Lab in Action


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Dancing Lessons

Perhaps our lab’s most well-known research is related to how native fence lizards respond to invasive fire ants. The idea of lizards “dancing” to avoid a fire ant attack has popped up across the internet (we’re on cracked! and many other sites). Arguably the most interesting part of this research is that lizards from populations that have co-existed with fire ants for many generations behave differently than those from populations that do not occur with fire ants.  In general, lizards from fire ant invaded sites frequently perform this “dance,” while lizards from sites that have not been invaded do so far less frequently.

This May, we focused on deconstructing this lizard dance. In addition to recording whether a lizard twitches in response to fire ant attack, we recorded what kind of twitch it performed. Sometimes it’s hard to distinguish between an arm kick, a leg kick, a full body twitch, etc,  but a little slow-motion helps us see what’s really going on. Check it out!

Pretty neat!

For many mornings during our first trip south, Sean, Chris, Mark H, and I ran behavior trials with the lizards we caught in the previous weeks. These trials, in short, involved placing a lizard on either a fire ant mound or foraging trail and recording any behaviors the lizard displayed. If too many ants crawled on the lizard, we stopped the trial so as to minimize undue stress. The trials lasted at most 60 seconds: plenty of time for the lizard to react should it be compelled to do so.

Fence lizard ready to dance!

Fence lizard ready to dance.

We actually tested each lizard on both a fire ant mound and a foraging trail to see if lizards respond differently in different contexts. This meant we ran over 200 behavior trials across 6 mornings!

Sean and Mark conducting a behavior trial.

Sean and Mark conducting a behavior trial. (It’s so exciting the photo is blurry!)

Sean, Chris, and some of our undergraduates recently began another trip south. During this trip, they will run  similar behavior trials with other native herps. Stay tuned for more updates from them!

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Herping in Happy Valley

While the lizard crew tours exotic locations like Alabama, Tennessee, and even the British Virgin Islands, and Jenny faces alligators while pursuing treefrogs in Florida, I spend most of my days at a farm in central Pennsylvania with some rundown barns. I should say, I spent most of my days there. My experiments just wrapped up, which is why I finally have time to contribute to the blog. I’ve mostly been occupied there with running tadpole experiments in pond mesocosms (essentially, fake ponds I make using 300 gallon cattle watering tanks) but I’ll talk about that another time. Like most research, my work (though worthwhile and punctuated with excitement) is full of drudgery and boredom: weighing and counting thousands of tadpoles, conducting many hundreds of behavioral observations, cutting down weeds, fixing and cleaning equipment. Often these activities are accompanied by downpours of rain or the sun beating down. Luckily, I’ve been able to enjoy my time out there the last couple years more than you might think. That’s partly because I have not been alone at the farm.

I’m not talking about the wonderful people I’ve had assisting me at various times. I’m talking about all the herps that have shown up on my little plot of land, in the barns nearby, and a hundred meters or so into the forest that my plot borders. I may not be in a particularly exciting place, but I’ve found 22 species of reptiles and amphibians there. Many of these were new to me, though they may be pretty plain to other people. Here’s a rundown, with some highlights about each find. Most of these pictures are mine, though not all were taken at the farm.

Eastern Milksnake (Lampropeltis triangulum) – This friendly little guy was just hanging out under an overturned cattle tank. This was a particularly exciting one for me. I’ve wanted to find a milksnake since I was a kid. They occur in Minnesota (where I grew up) but I never got to see any. As beautiful as I had hoped. The juvenile that Sean found just yesterday, though, blew this one out of the water in terms of beauty.

An Eastern Milksnake. Photo by Brad Carlson

Eastern Ratsnake (Pantherophis alleghaniensis) – I knew these snakes were in the barns because I’ve been finding their skins for a long time. Then last year, Dan Knapp and I finally caught one. They are the longest snakes I’ve got to see in the wild and are full of personality. It got better this year when Jennie Williams, Jason Langshaw, and I found them hiding in the rafters of one of the other barns. As many as six at a time! We are working on documenting something unusual we saw: they all shed their skins on the same day, and then disappeared from the barn. A clue to what might be happening is that the humidity peaked the day before, which could help them slough off the old skin.

An Eastern Ratsnake. Photo by Brad Carlson.

Eastern Garter snake (Thamnophis sirtalis) – They are abundant, and love hiding under my mesocosms. I rarely attempt to handle them, but not because of their bite. They often poop a foul-smelling musk that I hate intensely. You win, garter snakes.

Eastern Garter Snake. Photo by Brad Carlson.

Five-lined Skink (Plestiodon fasciatus) – The only lizard I saw, and I only caught a fleeting glimpse of its vivid blue tail before it disappeared into a pile of rocks and cement.

A Five-lined Skink. Photo by Michael Holroyd (Creative Commons License).

Wood Turtle (Glyptemys insculpta) – The only turtle, crawling through the woods along the trail we walk to study the Valley and Ridge Salamanders (below).

A Wood Turtle. Photo by Eugene Van Der Pijll (Creative Commons Licensed).

Spring Peeper (Pseudacris crucifer) – These little frogs are heard often and seen less. I found one trying to get into my mesocosms, perhaps hoping to lay some eggs in these convenient new ponds.

Calling male Spring Peeper. Photo by Brad Carlson.

Wood Frog (Rana sylavatica, aka Lithobates sylvaticus) – My main study organism, the tadpoles of which are used in all my experiments. Turns out, they also bred in a little pond in a small patch of forest surrounding by fields.

Calling male Wood Frog. Photo by Brad Carlson.

Green Frog (Rana clamitans, aka Lithobates clamitans) – One of these handsome frogs found its way into a kiddie pool that had once held tadpoles.

Green Frog. Photo by Brad Carlson

Northern Leopard Frog (Rana pipiens, aka Lithobates pipiens) – I used to see these everywhere growing up in MN, but not anymore. They are the species most famous for  declines in the Midwest and strange deformities. Happy to see that they are still around.

Northern Leopard Frog. Photo by Brad Carlson.

Gray Treefrog (Hyla versicolor) – One of my favorite herps. I kept a couple in an aquarium growing up. Their calls can be pretty loud when contained inside a bedroom. I think I named them after Lion King characters (my recollection: Mufasa and Nala or something like that. Timon and Pumbaa were the hamsters who, incidentally, hated each other.) At the farm, they are a bit of a nuisance: they will lay their eggs anywhere with water, including my experimental mesocosms. But it is hard to dislike their grinning faces. Plus, their tadpoles are very cool, with tails that turn bright red when predators are present: http://www.pitt.edu/~relyea/Site/Tadpole_movie.html

Gray Treefrog. Photo by Brad Carlson.

American Toad (Bufo americanus, aka Anaxyrus americanus) – Another common but charming amphibian. Since I had kiddie pools out this year, toads were able to get into them when I finished some of the experiments (and had not yet replaced the lids). The trills of amorous males were so relentless that it almost got to be annoying to a frogophile like myself. What I love about toads is how bold they can be though: unlike my main study organism (wood frogs), you can pretty much walk right up to a calling toad and he’ll still stand there with his throat proudly inflated.

A calling male American Toad. Photo by Brad Carlson

Spotted Salamander (Ambystoma maculatum) and Jefferson’s Salamander (A. jeffersonianum) – A few of these have shown up in the spring under the mesocosms before I move them into place. I’m not sure if they were resting in transit to/from a breeding pond or if this is where they stayed during the winter. Very hard to find them outside of the breeding season, so I count myself lucky.

A Spotted Salamander. Photo by Brad Carlson.

Eastern Newt (Notophthalmus viridescens) – On rainy days in the spring, newts start crawling around my mesocosms, hoping to gain entry. Somehow they can tell there is water in them, despite the fact that the tanks are about 2 ft tall. More surprisingly, they can get into the tanks! The sides slant outward, so I’m guessing they must do it when the weeds get tall enough for them to climb. Still impressive in my book (and annoying when running my experiments, since they like to eat tadpoles).

Eastern Newt. Photo by Brad Carlson

Valley and Ridge Salamander (Plethodon hoffmani) – These wormy little salamanders are common in the woods behind my field site. Common enough, in fact, that I have been working with Sean and Chris to study the natural history of these poorly-known plethodontids. So far we’ve found that they are quite different from their sister species, the better-known Redback Salamander (P. cinereus). Redbacks are territorial and faithful to individual shelter sites, whereas P. hoffmani wander from site to site, and seem to not mind sharing them with others. They are doves to the hawkish Redbacks.

Valley and Ridge Salamander. Photo by Brad Carlson

Wehrle’s Salamander (Plethodon wehrlei) – Jennie made this unusual find. Turns out, Wehrle’s Salamander is not supposed to be in that area! She’s documenting it now as a range extension for this species. Wehrle’s Salamander: it’s not just an Allegheny Plateau salamander anymore.

Plethodon wehrlei

Plethodon wehrlei (Photo credit: Wikipedia)

Northern Slimy Salamander (Plethodon glutinosus) – Likes the same area (and the very same hiding spots) as the Valley and Ridge Salamanders. It looks, however, like they come out later in the year (when it is warmer and drier) – about the same time the Valley and Ridge Salamanders begin to disappear as they seek refuge from the summer heat. It seems they’ve reached a timeshare arrangement.

Northern Slimy Salamander. Photo by Brad Carlson.

Two-lined Salamander (Eurycea bislineata) – Okay, I never saw this one. Chris claims he found one. I’d really like to see one myself – they look really cute in all the field guides.

A Two-lined Salamander. Photo by Jamie March (Creative Commons License)

Northern Dusky Salamander (Desmognathus fuscus) – I’ve found these denizens of the stream edge to be pretty flighty: overturn their rock, and they practically leap into the water.

Northern Dusky Salamander. Photo by Brad Carlson

Northern Spring Salamander (Gyrinophilus porphyriticus) – Justin Bohling’s herpetology class came out to the farm for us to lead them on a field trip. It was quite successful, turning up a total of 6 salamander species. We found a single juvenile Spring Salamander in the creek that cuts through the Valley and Ridge Salamander habitat.

Northern Spring Salamander. Photo by John D. Wilson (Creative Commons License).

Northern Red Salamander (Pseudotriton ruber) – This brilliantly-colored salamander was another find of the herpetology field trip.

Northern Red Salamander. Photo by Brad Carlson

Four-toed Salamander (Hemidactylium scutatum) – Chris and I were quite surprised to stumble upon a Four-toed Salamander sharing a shelter site with a Valley and Ridge Salamander. These unusual salamanders are specialists on mossy wetlands, where they lay their eggs in mounds of sphagnum. It was only after much wandering in the woods that we found any potentially suitable moss. In any case, this little fella seemed out of place.

Four-toed Salamander. Photo by Brad Carlson.

Well, that’s everything I can remember. With my dissertation research completed, I won’t be spending much more time out there at the farm. While I’m happy to be done with the long field days, I will miss the farm. Mostly because of all these little surprises that show up there.

Now if I took a trip down south, I suppose I could come up with 22 herp species in far less than 3 field seasons. But this is good enough for the Keystone State.


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120 seconds

Being caught by a large human can be stressful for a lizard, which means if we need a blood sample, we have to catch the lizard within a short time of their spotting us. This way we’re sure to capture their “baseline” hormone levels rather than the levels induced by a scary human leering at it. The blood samples we need to test the latitudinal cline with stress hormones that I described in my previous post all have to be collected within 2 minutes for this reason. Sometimes this is a difficult process! Here’s Sean catching a sneaky little lizard in Alabama. (Sorry for the shaky-cam! I couldn’t get too close for fear of scaring away the lizard.)

Relatively soon after collection, we have to spin down blood samples in a centrifuge in order to separate out and draw off the plasma, which contains the hormones. We have a handy dandy field centrifuge, but we’ll take power where we can get it!

Waiting for samples to spin down outside a visitor center in St. Francis National Forest.

Power is a commodity! Here I’m waiting for samples to spin down outside a visitor center in St. Francis National Forest, Arkansas.

The next step is to run assays on these plasma samples. We frequently run CORT assays in the lab (remember this?), so hopefully we’ll have this data soon!


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On Clines. And Victorian Men.

I really love reading books about early ecologists–or naturalists, as they were often called in the late 19th century. They have eventful maritime adventures and discover a wide variety of new exotic species. These young naturalists are always depicted as noble and inquisitive and have a much better sense of morality than their overly eager captains who are usually related to them. Okay, perhaps I read about fictional naturalists* more than the actual naturalists who shaped the field of ecology…which is kind of a shame, as the real ones were just as interesting! Darwin, Wallace, Hooker (and so many more!) are all pretty rad. Some of the early ecological and biogeographic  principles these early naturalists cooked up are still being tested–and, more often than not, supported–today.

Alfred Russel Wallace (Left) and Joseph Hooker (Right) looking dashing in their Victorian way.

Alfred Russel Wallace (Left) and Joseph Hooker (Right) looking dashing in their Victorian way.

Take, for example, Bergmann’s rule, which describes the latitudinal cline we find with body size: in general, organisms of a particular type are larger at higher latitudes where it is colder and smaller at lower latitudes where it is warmer. Bergmann suggested this is because large animals have a larger surface-to-volume ratio and thus less relative surface area over which to lose heat. This trend is common in birds and mammals, though of course there are exceptions. There is a similar cline with limb length and latitude (Allen’s rule – animals have smaller limbs in colder climates, in theory for similar reasons).

If you’ve made it this far, you’re probably wondering what this has to do with our lizards. Well, it is thought that there is a latitudinal cline with an animal’s baseline level of stress hormones. Some of our research, however, doesn’t seem to support this cline. Lizards at sites with fire ants have higher baseline levels of stress  hormones…which means we actually see the opposite of what this cline would predict!  One of the goals of our first trip this year was to collect blood samples from lizards at additional sites across the south (with and without fire ants) to help us parse out what’s going on. Chris and one of our undergrads will also be collecting blood samples from lizards in Pennsylvania and New Jersey to give us a much broader range of latitudes from which to consider this cline.

That meant covering a lot of sites in short time. Whew! It didn’t help that some of our sites weren’t as active as usual. One of our Tennessee sites has seen so much rain lately that the usual lizard sites were covered in over a foot of water!

Edgar Evins under water

Edgar Evins under water.

Still, Sean, Chris, and I managed to collect blood samples from enough lizards to keep our sample sizes happy…and we even managed not to kill each other while hotel-hopping across the south for 10 days! Success!

We caught a nice lizard on a tree at St Francis National Forest (AR). This timber rattler was waiting at the base.

We caught a nice lizard on a tree at St Francis National Forest (AR). This timber rattler was waiting at the base of that tree.

 *For an interesting read, check out The Voyage of the Narwhal by Andrea Barrett. It has nothing to do with narwhals, but rather follows a young naturalist and his soon-to-be brother-in-law on a journey to the Arctic and back. It takes a weird turn about halfway through, but it’s still pretty interesting.


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Stop! It’s herping time.

Did my last post really have no herps in it? That’s impressive, considering the number of cool herps we have recently encountered. Here’s a taste…

Sean with a black racer in Standing Stone State Park, TN.

Sean with a black racer (Standing Stone State Park, TN)

Pine snake near Solon Dixon in Conecuh National Forest, AL.

Pine snake near Solon Dixon (Conecuh National Forest, AL)

Green anole in Holly Springs, MS.

Green anole (Holly Springs, MS)

Sean impersonating a brown anole in Holly Springs, MS.

Sean doing his best impression of a brown anole (Holly Springs, MS)

We see a lot more than just cool herps, too. Sean and Chris do some birding in passing, and we certainly come across some interesting fauna in our travels…

Tiny chicken! in Geneva State Forest, AL.

Tiny chicken does not like strangers. (Geneva State Forest, AL)

Black widows give the best kisses. Good luck with that one, Chris. (Edgar Evins State Park, TN)

I’m not sure how this relationship will end. Good luck with that one, Chris.
(Black widow, Edgar Evins State Park, TN)