Sunday, April 8, 2012

Snake Escape



 The following article is a guest post by Michael P. Wines. Michael is a graduate student at Auburn University studying the Eastern Indigo Snake, Drymarchon couperi and the Red Hills Salamander,
 Phaeognathus hubrichti.  He was a zookeeper at the Memphis Zoo for several years after graduating from the University of Memphis.  When not being made a fool by study organisms (see below), he writes fiction. Michael recently had a short story published in a book, Summer Gothic- A Collection of Southern Hauntings and is a woodworker.

     I work with Eastern Indigo Snakes, Drymarchon couperi.  This non-venomous reptile is the largest native North American snake, capable of reaching over eight feet in length.  They are primarily snake-eaters and are often discovered eating rattlesnakes, Copperheads, Agkistrodon contortrix, and other venomous species. The huge reptiles were extirpated (driven to extinction in a certain area) in many places where they could once be found due to habitat loss and tortoise burrow gassing. In response, Auburn University, the Orianne Society, the States of Alabama and Georgia, and Zoo Atlanta are all working together to reestablish a population in southern Alabama.

The basic process is that snakes are hatched in captivity and raised for about two years. This is how long it takes for the snakes to grow to a size large enough to be fitted with radio-transmitters, which allow us to track how the snake is doing after it is released into the wild. These transmitters are surgically implanted a few weeks before we let them go. But, before they are completely released into the wild, the Indigos are put into three-meter wide tubs outfitted with an underground hibernacula (a refuge where a snake can spend the winter) and lots of hiding spots. The hope is that the snakes that are temporarily acclimated to the outdoors in these tubs will more easily adjust when they’re released into the forest.

We were going to release thirty Indigos two days from the time this story took place.  The snakes had been in the huge tubs for two weeks and everything was going according to plan.  This was the second year of releasing the snakes and lots of people had worked very hard for years to prepare for the coming day.

I went to take all the snakes out of the tubs because they needed to be examined by a veterinarian before being cleared for release. That’s when I realized that, somehow, one had escaped.  A buried drain-cover was messed up and the water from the spring storms pushed hard enough that it had popped off, leaving an escape route for the snake (completely my fault).  Luckily we had already surgically-implanted the snakes with transmitters, so there was still hope of finding it.

I picked up a transmitter receiver and went out to find said snake.  I got a beep after searching for only a few minutes.  I chased the beep for a little ways, maybe three hundred meters (1000 feet) down a hill, through a thick pine forest and to an armadillo hole on the side of a pond.  These snakes spend most of their time in Gopher Tortoise, Gopherus polyphemus, burrows, so finding the snake in a hole was not unexpected.  I set a wire funnel-trap at the opening of the hole and left to get some lab work done.

Later in the afternoon I went back to check the trap.  It was empty.  I tried the receiver again and got beeps from a different direction.  Crap.  The snake had left the hole and somehow missed my trap.  I followed the beeps for about ten-feet into the woods, then they got weak again.  So I turned in several directions to get a better reading.  It was the same.  I pointed the antenna at the ground, expecting it to be in another hole.  The beep got even weaker.  I scratched my head (with the hand holding the antenna).  The beep got stronger again.  What the heck?  I checked four directions and the ground again but only got the same results. 

I finally lifted the antenna higher, thinking it may be far off and I could get a better signal by reaching up.  It beeped louder.  After a few minutes of "fiddling" with the receiver I discovered the snake was about twenty feet (six meters) up a tree directly over my head.  These snakes rarely climb and when they do, they don't climb far.  I'd never heard of one being that high up before.

So, I decided to go up after it.  I really had no choice.  I had to get the snake back.  It was my fault it escaped and I was already feeling like an idiot.  I climbed about ten feet (three meters) up and used my monkey-like intellect to poke it with a long stick in an effort to coax it down.  I instead coaxed it across.  I managed to shimmy one tree closer and started again, still ten feet up.  This time it went down and across to a tall sapling.  I figured I could bend the tree down far enough to grab the snake.  I was right.  I started pulling the tree down, getting within three feet (one meter) of the frustrating, little punk.  The only thing I could do was put all my weight on the tree and ride it to the ground. 

It was effective except there was no ground.  I didn't consider the fact that I was almost over the pond again.  In a magnificent athletic leap, I grab the snake with one hand while still holding on to the weed of a tree with the other.  I dropped like one of Galileo's balls.  I landed on my back in the mud. 

I then, with my sudden adrenaline rush, jumped to my feet holding the snake up as if it were the baby lion king.  I yelled, "Who's the freaking biologist!?  I'm the freaking biologist!"  Then the snake simultaneously bit me and pooped all over me.

            I was so proud of myself that I thought I heard applause.  In fact, there was applause coming from the limnology (study of wetlands) class that showed up for some field work on the other side of the pond.  Who knew that a guy screaming how awesome he is after falling out of a tree into muddy water, then being bitten and covered in reptile feces, is entertaining?

            Two days later, the snake (along with twenty-nine others) was released into a suitable environment.  To this day, it is happily flustering the researchers charged with tracking the little Houdini through southern Alabama.  


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Want to Learn More?

Breininger, D., Mazerolle, M., Bolt, M., Legare, M., Drese, J., & Hines, J. (2012). Habitat fragmentation effects on annual survival of the federally protected eastern indigo snake Animal Conservation DOI: 10.1111/j.1469-1795.2012.00524.x

Friday, April 6, 2012

Friday Roundup - Hellbenders in Georgia, Frogs in New York City, and Rattlesnakes Nowhere to be Found

Hellbenders re-discovered in northwestern Georgia. A few years ago, I wrote about an unsuccessful trip to northern Alabama to look for Hellbenders, Cryptobranchus alleghaniensis. For a population of these large salamanders to survive over long periods of time, they need clean and undisturbed streams with lots of large rocks. Because of pollution, agriculture, and siltation, there are few of these streams left in Alabama. Hellbenders were never common in the State but, after a series of surveys for the species in the last few years, researchers concluded that they were gone. Extinct in Alabama.


But wait a minute...many people said the same thing about Hellbenders in northwestern Georgia, not far from the Alabama border. And, last month, a 14-year old kid fishing for catfish found a Hellbender on his line instead. Let's not start celebrating yet, a single salamander doesn't mean that there are many more animals in the area; we don't want to get excited before we know whether this is just a single and lonely individual or, better yet, representative of a thriving Hellbender population. But, in any case, it's encouraging news.


Lots of Excuses for Few Rattlesnakes. A couple weeks ago, rattlesnake roundups in Texas were quoted as saying that there were few rattlesnakes being rounded up. So few, in fact, that they felt the need to increase the bounty they paid for them. It didn't work. Roundup organizers said they were getting fewer rattlesnakes than usual because of the dry weather. Now Opp, Alabama has had to come up with a few excuses of their own. They are blaming their low numbers of rattlesnakes on warm weather. Dry weather, warm weather, drought, rain...it seems that some will go to great lengths to explain away rattlesnake declines as just another natural cycle. Time will tell whether the habitat destruction that we are causing (not to mention the roundups themselves) is having the bigger impact on rattlesnake population trends.


Alabama Turtles Protected. A few weeks ago I wrote about how Alabama herpetologists had sounded the alarm for freshwater turtles within the State. Throughout the southeastern United States, freshwater turtles were being targeted by commercial harvesters that intended to sell the animals for meat overseas. In response, several states, like Georgia and Florida, enacted rules to protect turtles from this type of harvest. Now, Alabama joins them.



Not a New Species
Alabama Researchers Help Discover a New Frog Species...In New York! We don't have to mount expeditions to South America or Africa for adventure or to find new species. There is plenty we don't know about or don't understand right under our noses. Recently, researchers investigating a frog making some weird-sounding calls determined this this frog, although it looked almost identical to other frogs in the region, was a new species. Get this, it lives in New York City.




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Want to Learn More?


S. P. Graham, & et al. (2011). Conservation Status of Hellbenders (Cryptobranchus alleghaniensis) in Alabama, USA. Herpetological Conservation and Biology, 6 (2), 242-249

Monday, April 2, 2012

Natural History of Neck-banded Snakes

The following article is a guest post by Andrew Durso. I would like to feature more guest posts here in the future; please contact me if you're interested in contributing. Want to see more posts from Andrew or other potential future guest bloggers? Encourage them by letting them know what you think in the Comments.

Andrew Durso currently lives in Logan, Utah, and is a Ph.D. student at Utah State University researching the physiology, ecology, and behavior of toad-eating snakes. Originally from North Carolina, he received his B.Sc. degree in Ecology from the University of Georgia, where he continually allowed the Auburn University Bioblitz team to triumph in herping competitions, in order not to injure their already low self-esteem (examples here and here). More recently, he completed a M.Sc. in Biology at Eastern Illinois University, studying methods to indirectly monitor snake diets. Andrew enjoys herping, bird-watching, cycling, and cooking. He hosts a blog on snake natural history at http://snakesarelong.blogspot.com/.


Also called Shovel-toothed Snakes or Skink-eaters, the members of the genus Scaphiodontophis are among the most unusually-patterned snakes. The one below should probably be called a neck-and-tail-banded snake, although I admit that's a little cumbersome.


As you can see, these snakes' patterns are just ridiculous. It looks like someone erased the middle third of a milksnake, or like a milksnake and a brownsnake had a love affair. But these snakes aren’t genetic freaks. There are likely some benefits to their unusual patterning, for reasons we can only guess.

Well, we can do a bit more than guess. In a 66-page paper published in the scientific journal Biological Journal of the Linnean Society, Jay Savage and Joe Slowinski examined the morphology (shapes and sizes), taxonomy (evolutionary relationships), variation, coloration, and behavior of Scaphiodontophis, and reached some very interesting conclusions.

Before we get into their findings, let us first describe their basic biology. Snakes within Scaphiodontophis are non-venomous, active during the day, and can most often be found within the leaf-litter of humid evergreen forests. They are unusual among snakes in North and South America because they have hinged teeth. It is thought that this tooth structure is useful for eating skinks and other hard-bodied prey. 
Eastern Slender Glass Lizard, Ophisaurus attenuatus
The tail of adult Scaphiodontophis is an incredible 39 to 49% of the total length. In other words, a 1-foot long snake could be about six-inches of tail. These tails have some other unusual features. Although they are disproportionately thick, they are surprisingly fragile, breaking off fairly easily. Just like many lizard and salamanders, Scaphiodontophis snakes probably drop their tails as an antipredator device. If a predator is distracted by a detached (but still wriggling) tail, the animal has a good chance of escaping. These behaviors remind me of the glass lizards of the southeastern USA (genus Ophisaurus), whose tails can be a whopping 50-75% of their total length and also detach fairly readily!

Now that we have a basic understanding of these snakes, let’s return to what I feel is their most unusual feature: their patterning. What is up with the coloration? At first glance, these snakes look like just another coral-mimic. Many snakes, such as Scarlet Snakes, Cemophora coccinea, are thought to look like venomous coral snakes because predators are less likely to try to feed on them. But that explanation isn’t completely satisfying for Scaphiodontophis. A closer look reveals pattern diversity that does not precisely correspond completely to any coral snake patterns. Individual snakes can have a pattern of tricolor monads (which are red bands separated by light-black-light), tricolor dyads (red separated by black-light-black), or even tricolor triads (red separated by black-light-black-light-black) or tetrads (red separated by...you get the idea). These bands sometimes extend along the entire body, are sometimes just on the front end, and are sometimes on the front and back ends but not the middle, as in the picture above. To make matters even more complicated, the black and yellow bands are sometimes offset so that they alternate with one another on the two sides of the body. Also, as if the "the extreme variability" (as described by Savage and Slowinski) wasn’t enough to confuse things, one snake’s patterning can change as the animal ages
!

In the 1950s and 1960s, biologists observed that several different Scaphiodontophis snakes that had previously been considered separate species could actually be found in the same places and were breeding with each other. That was when everyone realized that what they were using to distinguish between species probably wasn't accurate. This discovery led scientists to reclassify these animals as different species based solely on their based on neck pattern and coloration. This may have seemed like a good idea at the time, but the result was that populations of animals living far away from each other were considered the same species. Specifically, animals in Panama/Columbia and northern Central America were all considered S. annulatus, while everything in between those two areas was considered another species, S. venustissimus . This doesn’t make a lot of sense but it was the best we could do with the limited information we had. Because specimens of many neotropical snakes are still hard to come by, it is difficult to identify where the range of one species ends and another one begins.

Anyhow, Savage and Slowinski sorted all the existing Scaphiodontophis descriptions and synthesized the known information, as well as new information they collected on their own, and concluded that the situation wasn’t as complicated as everyone thought. They said that instead of two (or many) species, there really there was just one species with highly variable coloration patterns. In fact, their color patterns could comprise an entire new semaphore alphabet. 

Towards the end of their section on variation, the authors conclude that "No two Scaphiodontophis have the same coloration when head, nuchal (neck), body and tail patterns are considered in combination," which is pretty cool when you think about it. That pattern of these snakes is like a zebra’s stripes or a human fingerprint. A detailed system of notation for describing the color pattern of an individual Scaphiodontophis was developed by Savage and Slowinski, which for one snake looks like: wZ/B-6D-22/2M-S/2M/u+. Seriously.


So what explains all this pattern diversity? Well, the first question should probably be: why isn't the whole body banded? We have a partial answer to this question. This snake is an ambush predator, and it's typically found sitting motionless with the front of its body exposed and the posterior remainder buried in the leaf litter. At first, I didn’t buy that explanation, but check out this picture below, apparently taken in captivity, of a Scaphiodontophis in "typical diurnal posture".



Photo from Henderson (1984)
This apparently unique juxtaposition of behavior and microhabitat might be responsible for differences in the pattern on the snakes' bodies. That is to say, it is likely advantageous for the exposed part of the body to bear a banding pattern to mimic a coral snake because this would deter predators. However, this still doesn't explain why there is a disadvantage of having a banded back or middle body - but likely there is one, or else the entire snake would look banded (it is worth noting that there are a few populations in Nicaragua, Costa Rica, and Panama that are completely banded).

The inconsistent patterning could be because producing bright red, yellow, and black pigments is energetically expensive, but coral snakes and many mimics seem to do it just fine. I think it's more likely that the regional variation in patterning is due to regional variation in predator behavior, but that idea requires rigorous testing before we can conclude anything with confidence.

Like an Inflexible Chameleon
Studies have shown that coral snake mimics don't have to match the exact pattern of a coral snake very closely to convince predatory birds to avoid them. One way this has been tested was by puting out snake models in the forest. Different models had different color patterns: some looked like coral snakes, some didn’t, and some contained a mix of patterns. Scientists then counted which models predators tried to attack. They found that when predators see a model with a mix of patterns, they will direct attacks at the unbanded portion of a model. This could explain the partially-banded patterns we see in actual Scaphiodontophis snakes. So, although we may have some clues as to why these snakes look the way they do, if anything is to be learned from the history of research on Scaphiodontophis, it is that nothing about these incredibly interesting snakes is as simple as it seems. 




Thanks to photographers Silviu Petrovan, Mauricio Rivera, Pierson Hill, Jaroslav Vogeltanz, and Jairo Maldonado for the use of their photos, and to Dave Steen for inviting me to guest write this article.
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Want to learn more? Check out the following scientific articles



SAVAGE, J., & SLOWINSKI, J.B. (1996). Evolution of coloration, urotomy and coral snake mimicry in the snake genusScaphiodontophis(Serpentes: Colubridae) Biological Journal of the Linnean Society, 57 (2), 129-194 DOI: 10.1006/bijl.1996.0010

SAVITZKY, A. (1981). Hinged Teeth in Snakes: An Adaptation for Swallowing Hard-Bodied Prey Science, 212 (4492), 346-349 DOI: 10.1126/science.212.4492.346
Henderson, R. 1984. Scaphiodontophis (Serpentes: Colubridae): natural history and test of a mimicry-related hypothesis. Special Publication, University of Kansas Museum of Natural History 10:185-194.