The Lizard Log

The Langkilde Lab in Action


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Solon Dixon!

Hey everyone!

Even though I am continuing the same project from last year (how maternal stress affects the offspring in fence lizards), there are still some striking differences. One of the biggest is that there are fellow grad students and a post doc this summer!

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From left to right: Cameron (PhD), myself (PhD), Kirsty (post-doc), and Dustin (PhD).

Also, last year we made the drive in one day, however this year we broke the drive up over 2 days. This gave us an excellent opportunity to experience different parts of the USA on our drive. For the night we stopped in Knoxville, TN and had dinner at an amazing place called Calhoun’s On The River. True to its namesake, it had a beautiful view of the Tennessee River!

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After all the driving, we finally made it back to Solon Dixon and started catching lizards. As usual, the lizards’ personalities were very evident.

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Male fence lizard unamused with our attempts to catch him

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Apparently the female lizards found that corner of the tub to be very interesting.

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As I went to put this female back in her tub, she refused to let go of my fingers!

On top of finding many fence lizards, we were also about to see many other reptiles and amphibians!

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A barking tree frog tightly hugging my finger.

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An American alligator, at a very reasonable size to handle.

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A yellow bellied slider who found a little bit of water to sit in.

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A glass lizard!

As I spend more time down here, I find it rubbing off on me more and more.

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Very tempted to get a cowboy hat.

After catching the females, our first trip came to an end. However, we were quickly back down to release the females and run experiments with the hatchlings. With us this time we had an undergraduate researcher, Jen!

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The Bayfront Park, overlooking Mobile Bay. Located right next to one of our field sites, Blakeley State Park.

As we wait for more hatchlings to emerge, we have been focusing on removing fire ants from some of the enclosures we built. As fire ants are highest in the mounds earlier in the day, this means some early mornings. On the up side, it also means we always get to see the sunrise.

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Sunrise right near the enclosures.

Most things have gone well, with only one piece of equipment starting to show signs of wear, but this just gave me an excuse to do some handywork!

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Used some steel epoxy to seal a leak in the pot we boil water in for fire ants.

Things have started to pick up in terms of hatchling, so soon you should be able to hear about how things are going with them. Until then, here is a pic from right here at Solon Dixon

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With the drier weather they are finally able to do prescribed burns.

Cheers,
David

 

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The Natural State

Happy Memorial Day!

I am happy to report that the “uninvaded” team has returned to PA, lizards in hand–or bag as it were. Our team, consisting of Braulio,  Caty, and myself, traveled to Tennessee and Arkansas. Arkansas prides itself on being “The Natural State” for its “natural scenic beauty, clear lakes and streams, and abundant wildlife.” I can’t speak to most of that, but it does have lizards!

Fence lizard with a regenerating tail.

Fence lizard with a regenerating tail.

Rainy and overcast days slowed us down a bit. As ectotherms, lizards rely on external sources of heat, which means they like to bask in sunny spots in order to warm up. The thick clouds didn’t provide many good basking opportunities, but thankfully a few lizards made an appearance in the brief moments of sun.

Sometimes fence lizards like rocky habitat.

Sometimes fence lizards like rocky habitat.

2blendinMany other lizards like to bask on trees.

We did see a few sunny days, which gave Braulio and Caty the opportunity to catch their first lizards.

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Braulio with a Tennessee lizard.

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One of Caty’s first catches!

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Lizard selfies are the best selfies.

We even managed some “expert” catches, on more than one occasion slowly driving by a basking lizard and noosing it through the open car window.

Because we were looking for females, we of course became experts at catching males. One male lizard really hoped I was a tree. We tried to return him to his log, but on two separate occasions he ran up my leg. Sorry little guy!

Nope, not a tree.

Nope, not a tree.

Another male, pictured below, really surprised me. Lizards vary in coloration, but not usually by much. I’ve never seen a fence lizard so dark!

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A very dark fence lizard. His chest badges were impressive as well!

After two weeks of catching, we headed back to the lab. Our females are now happily housed in their nesting boxes, and one has laid her first clutch of the season. We’re all excited to see the resulting hatchlings!

Check back soon for more stories and photos from the field as well as updates on the specific research projects happening this summer.

We even spotted a fence lizard on a fence. So satisfying. A fence lizard on a fence. So satisfying.


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But Do They Make Omelets?

Short answer: Nope. Fire ants like their lizard eggs raw. Our recently accepted paper in the Journal of Herpetology “Invasive Fire Ant (Solenopsis invicta) Predation of Eastern Fence Lizard (Sceloporus undulatus) eggs” shows that fire ants do indeed eat fence lizard eggs in a natural setting, but, despite being known as “fire” ants, these hymenopterans haven’t quite mastered the art of cooking their food prior to chowing down. Get your non-final, still with a couple of mistakes, pre-print copy online (paywalled) or download one from this blog (posted for personal use of our readers courtesy of SSAR)!

At this point, you may be asking yourself, “Why should I care if fire ants eat fence lizard eggs?”, so I’ll discuss the impetus behind this project. Previous research in the lab had given us a good idea of how fire ants can impact juvenile and adult fence lizards: they are found frequently on the ground by fire ants, stung if they don’t run away, and can be envenomated when eating fire ants. BUT we knew incredibly little about what impacts fire ants might have on one unexplored life stage of fence lizards: eggs! And unlike juveniles and adults, these eggs can’t flee or twitch when attacked by fire ants; they remain in a nest for 55-70 days (depending on site and temperature), during which time they might be vulnerable to fire ants. Additionally, fence lizards often (though not always) prefer sandy sites with low canopy cover, where sunlight can warm the nest, exactly the type of microhabitat beloved by fire ants. And fence lizards build their nests 4-8 cm underground, right at the same depths where fire ants construct their underground foraging tunnels. We surmised that fire ants might come into contact with fence lizard eggs with some frequency, and, if fire ants ate the eggs, this might have a large impact on fence lizard populations.

Fire ants are known to eat the eggs of other reptiles, including those of snakes, turtles, and some lizards (such as anoles). To determine if fire ants were physically capable of eating fence lizard eggs, Jill Newman (a former lab undergrad who just started her master’s at Clemson…wooooooo!), Tracy, and I designed a small experiment. We presented fence lizard eggs to captive fire ant colonies and observed them penetrate the eggs in less than 30 minutes…a rather dramatic response! However, we also wanted to see whether fire ants might eat fence lizard eggs under more natural conditions. To address this, Jill dug holes in the ground to the depth of fence lizard nests and placed 12 eggs near fire ant mounds overnight. Upon examination, 11 of the 12 eggs had been punctured and eaten in less than a day!

The next summer, I designed a follow-up experiment to learn more about this type of predation. Specifically, I wanted to know how many eggs fire ants might eat, how quickly they might find them, and whether any environmental variables, like distance of a fence lizard nest from a fire ant mound, might affect predation. To address this, I started by collecting fence lizard eggs. A LOT of fence lizard eggs (over 150!…I resisted the urge to make my own omelet).

I couldn’t, however, just bury the eggs in the ground and check them after 24 hours (as Jill did) to answer my question about how long eggs might survive…I had to be (a little) creative. After reading about a similar problem faced by Kurt Buhlmann and his solution when he wanted to monitor turtle eggs, I developed a method allowing me to monitor the eggs daily without disturbing them (which might attract fire ants and increase predation).

For each nest, I dug a hole into the ground and sunk into it a clear, capped acrylic tube. I carefully replaced the sandy soil around each tube and placed six eggs (a small, but reasonable size for a fence lizard nest) next to the tube. I inserted a small piece of plastic transparency above the eggs and then carefully covered the whole arrangement with the soil. The transparency prevented soil from entering between the eggs and the acrylic tube, and, by lowering a video camera into the tube, I could count the eggs and see if they were being attacked by ants (or other predators). At each “nest” I also measured the amount of canopy cover and the distance to the nearest fire ant mound.

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Diagram of nest tube with camera for viewing eggs underground.

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…aaaaand what one of them looks like in the ground.

Each day, for up to 20 days, I monitored the nests and recorded if all the eggs were present. If I found ants attacking the eggs, I waited a few hours to let them eat the eggs (or at least let them make a start) and then dug up the nest to catch and identify some of the ants. I can definitively say that fire ants do not like to be disturbed when they are in the middle of a meal! Because of our innovative setup, it only took about 3 minutes a day to monitor each nest (check out a couple of examples below).

In our trials, we found that 24% of nests were attacked by fire ants within 20 days. Extrapolating this to the full incubation period of fence lizards using a mathematical model, we estimated that up to 61% of fence lizard nests are in danger of being preyed on by fire ants. We also did not find any relationship between how far nests were from fire ant mounds and how likely they were to be eaten. Given the high densities of fire ants at many areas in the Southeast, it seems likely that fire ants prey on a substantial portion of fence lizard nests in the wild. Of course, we know that fence lizard populations where we do our research are not in danger of disappearing. Fence lizards are doing fine even in the face of this predation, which is great news, and suggests that survival in other parts of a fence lizard’s life or high reproductive output may allow them to persist in fire ant invaded areas. In the future, I am aiming to build mathematical population models to understand the impacts of egg predation by fire ants, and see how this predation may affect populations over the long term.

One other point of note is that, for many species of southeastern herps that are declining, such as kingsnakes or southern hognose snakes, fire ants are often suggested as a culprit without any definitive proof. My project suggests that fire ants can indeed prey on large portions of the nests of some species, but also shows that one species is doing just fine even when fire ants may be making a buffet of about half of its nests. Moving forward, I would recommend that lab and field trials like those we’ve done be used to pinpoint if fire ants are indeed a threat to the eggs of these other species, and, if so, what proportion of nests are at risk.


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Gearing up for SICB!

Happy New Year!

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New year, new beginnings. And hats. Lots of hats.

As we start to wrap up our holiday break, Chris T. and I are preparing for a trip to Portland, Oregon for the 2016 annual meeting of the Society for Integrative and Comparative Biology (SICB). We will both be presenting talks on Monday.

I will be expanding on results I presented at ESA in August, which address how stress (fire ants) experienced in early life or in previous generations affect adult physiology and immune function in lizards. My talk is Monday, January 4th at 11:15 in room B110/111.

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Chris will be sharing his results from SSAR with a new audience. He will discuss how invasive fire ants have reversed geographical patterns in fence lizard ecology, including their behavior, stress responses, and morphology, across their range in less than 75 years. Chris’s talk is also on Monday, January 4th at 11:30 in room B114. A determined Langkilde Lab follower could attend both talks back to back in nearby rooms! 🙂

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Come say hello if you will be there!


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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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Alabama Part II: Prep for experiments!

Hello again! After my first trip down to Alabama, I ended up catching a lot of gravid female fence lizards. I ended bringing them back to Penn State so they could lay their eggs.

Individual housing so we could figure out who laid which eggs

Individual housing so we could figure out who laid which eggs

They took to their new homes very well, as they were furnished with a half log for basking/hiding, and sand for laying their eggs.

She wasn't going to share her new home with anyone!

She wasn’t going to share her new home with anyone!

We spent most of every day with them, whether it was cleaning their housing, doing behavioral observations, checking for eggs, or feeding them.

You can imagine which part was their favorite!

You can imagine which part was their favorite!

It took nearly a month for all the mothers to lay their eggs, and it was not without excitement. Most of them laid their eggs in the nice, moist sand we provided, and their eggs looked wonderful. However some decided to rebel against that idea and laid their eggs directly under the heat lamp! Needless to say, those eggs needed some TLC.

Finally, when it was reaching about the time for the eggs to start hatching, we headed back down to Solon Dixon, AL to get ready for the second round of field work. I brought 2 volunteers with me again, and they have been an incredible help, not only with doing the work down here, but also giving great ideas and making the trip much more enjoyable.

Lexi (L) and Michaleia (R)

Lexi (L) and Michaleia (R)

The first order of business was returning the mothers back to where we caught them. Luckily, they all posed for me to take nice picture,

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Lizards going back home!

After the mothers were safely back to their natural habitats, we got started on the biggest part of the preparation phase, making the outdoor enclosures. To do this we used aluminum fencing buried 6-10 inches into the dirt, supported by metal electrical poles. To make our lives easier, we rented a trench digger to dig the trenches for us!

Imagine a giant skillsaw that you pull behind you.

Imagine a giant circular saw that you pull behind you.

Using that helped speed up enclosure building a lot, especially since we had 4 to build.

The finished product.

The finished product.

Even using the trencher, it took many long, hot days in the field to get everything ready. Luckily there are a few cool and refreshing escapes close by!

A freshwater spring at Solon Dixon.

A freshwater spring at Solon Dixon.

We returned once again to the spring at Solon Dixon, whose 60F water made the 100F days much more bearable. In addition to the cool temperature, the spring also has a wealth of different organisms. This time, in addition to all the fish and spiders, we saw a crawdad and a frog!

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Also, while waiting for some aluminum flashing to come in, we were able to take a short trip to Destin, FL. The sand and water were beautiful, and the amount of fish, jellyfish, and invertebrates (with a surprise appearance from a shark!) was incredible.

O'Steen Beach

O’Steen Beach

But after the relaxation time, it was back to work. Once the enclosures were up, we had to remove the fire ants from half of the enclosures to give us high and low stress enclosures.

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The “Fire ant removal” gear.

To do this, you pound a piece of metal into the colony, and then flood it with hot water. Around this time, we started seeing wild fence lizard hatchlings.

A little guy trying to blend in with white rocks....he will learn how to blend in better!

A little guy trying to blend in with white rocks…    he will learn how to blend in better!

With those sightings, we knew that our hatchlings would be next. And sure enough, a few days later, we had our very first eggs hatch.

3 little guys just hatching.

3 little guys just hatching.

Now that the hatching has started, we get to start stocking the enclosures with baby fence lizards and running behavioral trials. I am very excited to be able to finally run experiments with the hatchlings! I look forward to letting you all know how the experiments went.
Till next time,
David


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Panhandling in Florida

While it still seems like the weather is feeling March Madness here in State College, with all our wavering between warm and cold, rain and snow, I spent a couple of days of my spring break in the panhandle of Florida, camping, letting my skin remember what humidity is, and, of course, herping! While the only herps I’ve seen up North so far are spring peepers, the season is considerably more advanced down South. In the Apalachicola National Forest and surrounding areas, I encountered temperatures >80 degrees, trees with leaves, and even got a mild sunburn. In the midst of driving to campsites and hiking, I also stumbled on a small sampling of the huge herp biodiversity present in this forest.  The first herp I came upon was this juvenile cottonmouth (Agkistrodon piscivorus) on the road to my campsite. His stopping in the middle of the sand road made him a nice target for a huge pick-up barreling down the road, but, after some creative car parking and arm waving, I managed to convince the other driver to leave this little fella in a non-flattened condition.

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Not old enough to have any hairs on his chinny-chin-chin. This little bugger was all of 16 inches.

As I prepared to use my handy snake hook to help him off the road, this snake was kind enough to give an open-mouthed smile for the camera with a cottonmouth’s trademark, white grin.

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No, I was not dangling any delicious rodents just out of the frame.

Much of the forest consists of pine flatwoods, but there are also sandhill areas and intergrades between these habitat types. In these areas, I found plenty of our old friends, the Eastern fence lizards (Sceloporus undulatus). Both males and females were out basking, and in some cases, beginning to establish territories for the upcoming season. I also found a young male with fully developed badges who was only 44 mm long (snout-vent length)…an early bloomer!

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A male fence lizard surveying his domain.

In the amphibian category, I turned up a few Southeastern slimy salamanders (Plethodon grobmani) by rolling over downed logs (and carefully replacing them!). This species is part of the slimy salamander complex and has a neat pattern of white blotches underneath and golden flecks above.

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I also traveled to Ochlockonee River State Park in Florida, right next to both the National Forest and St. Marks Wildlife Refuge. This was a neat little state park with a few trails and some great opportunities for canoeing/kayaking on the river.

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The view from the riverside trail in Ochlockonee River State Park.

The park also had some interesting animals, including even a mammal, the generally rare, but locally common white squirrel! These squirrels are just mutants of the normal Eastern gray squirrels (Sciurus carolinensis), that were introduced to the area within the past century. They’re not albinos, as they still have pigments in their eyes and usually a darker stripe down the back, but they do appear rather striking. I had no idea that these squirrels were in the park, so I was initially pretty surprised to find one hanging out right next to my campsite.

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A slightly blurry picture of one of the white squirrels in the park. You can see the dark eye and beginning of the darker back stripe in this photo. Other squirrels seem to treat them normally, as the normally pigmented gray squirrel seen here was doing his best to court the white one!

Of course, the park also has an abundance of herps. I came across several barking treefrogs (Hyla gratiosa) on the sandy trails at night as they were moving to and calling in the flatwoods ponds.

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A barking treefrog pauses for a quick snapshot before continuing its journey to a nearby chorus.

The last herp of the trip in Florida was the same as the first, a juvenile Cottonmouth crossing the road. This one picked the same characteristic posture as the first and also had a very pretty yellow tail tip which is common among some juvenile pitvipers.

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I also found several other species, including oak toads, southern toads, southern leopard frogs, bronze frogs, ornate chorus frogs, and an eastern diamondback rattlesnake (which didn’t sit still for long enough to grab photos), and a very squashed pigmy rattlesnake (which sat too still…:*(

As field season ramps up in the lab, we’ll have more research updates right here (as opposed to updates on recreational herping).

In other news, the lab is also preparing to send a contingent to the annual meeting of the Society for the Study of Amphibians and Reptiles (SSAR). After dominating the awards last year, we’re off to a promising start this year. Both Mark Herr and I received 2015 SSAR Conference Grants from the Gans Collections and Charitable Fund covering our registration fees for the meeting! We’ll have more news on that front this summer!