In this fifth installment of the human stories behind herpetological research, we hear the story behind a 2014 Natural History Note in SSAR’s Herpetological Review from one of the note’s authors, Sean Graham. If you like Sean’s account–focusing on the science and filed adventures behind herpetology–you should purchase his excellent new book, American Snakes.
The citation for the note this story is based on is as follows:
Newman, J. C., T. Robbins, and S. P. Graham. 2014. Sceloporus undulatus (Eastern Fence Lizard). Envenomation. Herpetological Review 45:133-134.
SSAR members can access the article here. Enjoy Sean’s account below!
Probably my favorite Herp Review note I was involved with was back in 2012, when I was a postdoctoral student in Tracy Langkilde’s lab at Penn State. Langkilde studies interactions between fence lizards (Sceloporus undulatus) and exotic fire ants, showing that in areas where fire ants have been established longest, the lizards have evolved longer legs and behaviors appropriate for escaping ants. So, we were scouring the woods catching fence lizards in areas where fire ants are well-established (southern Alabama) and also in areas where fire ants are absent (northern Tennessee and Arkansas) for various comparisons. Fence lizards are often common in areas where there is a considerable human footprint: our best sites were often farms, backyards, or junkyards with open habitat edged by trees and woodpiles. At Geneva State Forest in Alabama, we made a beeline for a campground near the lake, which had a park-like area with widely spaced trees. And, for us, a goldmine: a junk pile with big piles of old wood and boards.
Right away we saw a fence lizard perched atop a pile of boards. It was in the standard, upright, alert posture of basking fence lizards. We got our nooses ready.
The best way to catch a fence lizard is with a lizard noose: a long pole with a small loop of dental floss at the end. In our case we used fiberglass, collapsible, reel-less fishing rods you can get at Walmart. Locals often gave us strange looks and even overcame their reluctance to ask us what in the hell we were doing stalking the campgrounds looking at tree trunks carrying strange fishing poles. Our nooses lacked the rings of real fishing poles and extended some 20 feet. We usually only used the last two segments of the rod but kept the extra-long sections in our vehicle in case we found a particularly elusive lizard. We called this one the “big daddy”. For this lizard, we didn’t need the big daddy, and instead walked slowly up to it and got the noose around its neck. Soon we had it in hand. But something was amiss.
A fang protruding from the dead fence lizard. (c) Sean Graham
The lizard was decidedly dead. We looked it over at every angle, and even though the lizard had seemed alert, it was positively deceased. Our first clue to the developing mystery was that its belly appeared bruised and discolored. Then somebody noticed something protruding from its back. I looked it over and couldn’t quite tell what I was looking at. It almost looked like some worm emerging from the animal, so our first suspect was a botfly. Occasionally, lizards like anoles fall prey to these despicable, flesh-eating parasitoids. But they are usually large and look like big maggots, so we quickly cleared flies as a suspect. I pulled out a pencil to probe the object, and it fell into my hand. It was curled, hollow, and needle sharp on one end. The murder weapon.
“This is a pitviper fang,” I said, looking down around my feet. I saw a perfect flat board at the bottom of the pile. “There’s going to be a copperhead under there.”
I lifted the board, and sure enough, reveled a copperhead.
The culprit: a copperhead. (c) Sean Graham
From what we know about pitviper hunting tactics, we deduced that the lizard had been scurrying around the boards earlier that morning, and the copperhead ambushed him. Probably while struggling to get free, the lizard broke the copperhead’s fang and ran off. Normally the snake would have struck the lizard and held on, swallowing it after the venom incapacitated the lizard. Pitvipers also strike and release prey, then use their tongue to search out the victim after it has died. The snake was unable to track down the lizard, possibly because of the trauma of losing a fang. The lizard then proceeded to bask in the sun, an interesting behavior consistent with what we know about the immune response of snakes and lizards; there is evidence that reptiles bask when they are sick because immune function is more efficient at hotter temperatures. By the time we got to the lizard that morning, the venom had finished him.
These kinds of chance observations are invaluable for understanding our natural world. Pitviper hunting tactics are so difficult to observe that they have only recently been systematically studied using expensive technology such as radio transmitters and high definition videography. And an intensive study on copperhead hunting may never have revealed such an interesting, idiosyncratic misfire.
The author, practicing his noosing skills and contemplating his next Natural History Note for Herpetological Review.
We started writing down various details in our field notebooks. Time of day, date, etc. We got measurements from the lizard and measured the distance between the snake and lizard. We collected the lizard in one of our cloth bags and eventually accessioned it into the Auburn University collections. We collected the fang in a small vial we used for storing lizard blood. We had what we needed to write up a note. However, we couldn’t confirm that the copperhead we found was the killer (by checking to see whether it was missing a fang) because we didn’t have any of the proper equipment for handling venomous snakes. So, our case was based mostly upon circumstantial evidence.
The most challenging thing about reporting this observation was that I wanted the note to reflect how we systematically figured out what had happened, including the Holmesian prediction that a copperhead did it. The way the notes are formatted, it is sometimes hard to tell the story the way it really went down. Fortunately, the editor was kind to us and we were able to include enough detail to make it clear how we used good, old-fashioned police work to find the killer.