Monday, November 26, 2012

The Alligator Snapping Turtle: Natural History, Mythology, and Conservation

The following article is a guest post by Brian Folt. Brian is a Ph.D. student at Auburn University, where he studies the community ecology of amphibians and reptiles. He grew up in the Midwest and received a B.S. from Ohio University in 2011. Brian conducts field research in the southeastern United States and Central America. Brian is an avid outdoorsman and a die-hard Cleveland sports fan. You can follow him on Twitter @brianf0lt.

     Here in the United States, few are aware that we actually live alongside one of the most species-rich turtle faunas in the world. Of 320 species known worldwide, 42 inhabit the southeast US, with a hot-spot of at least 18 known from the Mobile River Delta in Alabama. Only the Ganges River drainage in eastern India has a similarly-sized area with more turtle species (but just barely!).

     Turtles of the southeast vary drastically in ecology, natural
 history, and morphology. These animals inhabit a diverse spectrum of habitats, from well-drained pine forests, like the Gopher Tortoise, to high elevation bogs, like the tiny Bog Turtle. Of this diverse turtle fauna, perhaps the most remarkable species is the Alligator Snapping Turtle (Macrochelys temminckii). The largest freshwater turtle in North America, this species is also highly aquatic. Unlike classic riverine turtles which conspicuously bask on logs or shoreline, Alligator Snappers never leave the water to bask or move overland, except when females lay eggs (an annual occurrence) and juveniles move from these nests to the water.

      Alligator Snapping turtles are thought to be sit-and-wait predators: they hang out patiently on the river bottom with mouths agape, waiting for food to come to them. They possess a fleshy structure on the tongue, the lingual lure, which attracts fish or other prey to the jaws. When inquisitive prey touch the sensitive lure, the powerful jaws immediately snap shut, and the turtle receives a nice snack. Bon app├ętit!

      I spent last summer in the bayous of south Alabama trapping turtles with Jim Godwin, a biologist with the Alabama Natural Heritage Program at Auburn University. Jim is conducting a long-term study of the federally-endangered Alabama Red-bellied Turtle (Pseudemys alabamensis). During this work, however, we also became intimately familiar with Alligator Snappers, as we caught over 40 of these fascinating turtles.

     Throughout the summer, we had the pleasure to talk about our work with many local swimmers, kayakers, canoeists, fisherman, etc. Curious folks generally ask a series of questions regarding the Alligator Snapping Turtles, questions mired in mythology. Here are a few typical questions and the answers I often provide:

How big do they get? 

     Big! Really big. The largest records indicate that some 
male Alligator Snapping Turtle shells can reach 30 inches [0.76 m] long and some whoppers can weigh more than 260 pounds [118 kg]! That’s heavier than Cam, or four scooters. The largest individuals we’ve captured weighed approximately 150 pounds [68 kg]. Because males have different tail proportions and get much larger than females (females generally don’t get much bigger than 77 pounds [35 kg]), this species has what is called sexual dimorphism.

How long do the loggerheads live? 

      “Loggerhead” is a common name that many locals call the Alligator Snapping Turtle. This of course creates confusion because of the large, endangered sea turtle with the same name. Confusion aside, people always wonder how long Alligator Snappers live, and the answer is a long time. Some individuals have lived 70 years in captivity, but we really don’t know how long they live in the wild. Studies have counted rings on shell scutes (“annuli”) to estimate turtle age, not much unlike similar studies of trees or fish. The scute measurements indicate that individuals easily reach ages into the 40s, but estimates beyond this point are unreliable. More long-term mark-recapture studies are needed to determine how long this animal can live in the wild.

Are you going to eat them? 

     No! That’s illegal (and gross). All turtles are protected 
from collection in Alabama, and for good reason. Commercial harvest of Alligator Snapping Turtles in the 1960s and ‘70s by soup companies appears to have severely depleted populations throughout the species’ range. More recently, trappers have been exporting other local turtles to China, where they are highly valued for food and medicine. Because turtles are an important component of balanced freshwater ecosystems, we are attempting to protect and conserve them in Alabama.

But, what are the chances that I’ll be bitten while out for a swim? I’ve heard they can take your foot off! 

     While this may come as a surprise to many, the answer is none! As far as we know, there is no documented case of a hidden Alligator Snapping Turtle biting a swimming or bathing human that is minding their own business. Like most wild animals that encounter people, it seems that the first reaction of Alligator Snapping Turtles is to flee. For these reasons, I’m highly skeptical that an innocent swimmer will ever be bitten.

     Of course, if you pull one of these beasts out of the water, it’s a different story. Like all wild animals, these turtles will defend themselves when cornered and those jaws are no joke. Dr. Peter Pritchard’s classic monograph, The Alligator Snapping Turtle: Biology and Conservation, provides a photograph of a Florida citizen who lost the tips of his middle and ring fingers to a bite from a captive animal. If you are afraid of being bitten by an Alligator Snapper, don’t play around with them! The same concept applies to venomous snakes.

     Through our research efforts, we have learned much about the distribution and abundance of Alligator Snappers in Alabama, and answered a few interesting questions about the effects of historic commercial harvest on this species. In general, it seems that Alligator Snapping Turtles are currently rare in Alabama, but there are a few places where the species remains locally abundant. Unfortunately, despite legal protection in Alabama and throughout its range, this species is occasionally killed by abandoned fishing lines, such as limb-lines or trotlines. This has been a major cause of turtle mortality in Georgia and may inhibit the recovery of populations in Alabama. I urge fisherman, officials, and civilians to more closely monitor and regulate these fishing lines to reduce the by-catch and mortality of the Alligator Snapping Turtle, a truly magnificent component of our native wildlife.


Want to learn more? Check out these sources:

Buhlmann, K., Akre, T., Iverson, J., Karapatakis, D., Mittermeier, R., Georges, A., Rhodin, A., van Dijk, P., & Gibbons, J. (2009). A Global Analysis of Tortoise and Freshwater Turtle Distributions with Identification of Priority Conservation Areas Chelonian Conservation and Biology, 8 (2), 116-149 DOI: 10.2744/CCB-0774.1

Sunday, November 18, 2012

Rattlesnakes In My Yard: Is Relocation a Death Sentence?

           For many people, finding a rattlesnake in the yard does not present much of a dilemma. They just kill it. But, for those people that appreciate rattlesnakes and don’t want to kill them all, encountering one of these venomous animals near the house raises an important question: What now?

            A rattlesnake around the house is a risk that most people just don’t want to take. And, that’s understandable. Inevitably, the topic of relocation is raised as a humane alternative to killing the animal, which is likely just traveling through or was attracted to an abundance of rodents. But, a letter from a reader summarizes a common concern.

A Timber Rattlesnake Relocated by Gary L.
I live in northeast Alabama outside of Scottsboro at the base of a small mountain ridge.  A rocky ravine runs down the mountain right to my backyard.  When I walk out of my back door I am automatically herping (i.e. finding a lot of amphibians and reptiles).  Occasionally a timber rattler will show up.  Since I have several small dogs and don’t want the snakes so close to the house, I relocate them.  I have a good set of tongs and snake bag and can relatively safely handle the snakes.  Initially I took the snakes to a secluded area about 5 miles away.  My conscience started to bother me because I knew that the snakes would not be able to return to their proven den site.  Since then I have taken several snakes a short distance backup to the top of the mountain ridge and, I’m sure, in range of their den.  Now I’m concerned about the snakes being able to find their way back to my backyard.  My question is: ‘Is it a death sentence for the snake if I move it far enough away from its range that it cannot get back to its den?’   


Gary L.

            As Gary notes, rattlesnakes do not just spend their lives randomly crawling across the landscape.  Timber Rattlesnakes (Crotalus horridus) often use den sites throughout their lives. The use of these dens isn’t just a matter of convenience; the rocky and underground caverns are necessary for the snakes to survive the winter in colder climates. These areas provide protection from the cold and from predators. In the fall, females will give birth around their dens and the young benefit from the security of the rocks and also from having a lot of adult rattlesnakes around.

            Timber Rattlesnakes do sometimes disperse from their “home” den and reach other dens to mingle with new snakes, but the point is that there are often unique features of the landscape that are necessary for a snake to survive and these features are well-known by individual snakes that spend their lives in the same general area.

            So, as you might expect, relocating a rattlesnake away from your house isn’t automatically a humane option at all, it may just be dooming that snake to die a slow death in the woods as it crawls around looking for something familiar.

            One short-term option is to relocate snakes only a short distance from your house, perhaps less than 1000 feet (roughly 300 m). This technique moves the snake away from your home but allows the animal to stay within the forest it knows and close enough to its den that it can easily return. As Gary noted, this means that the snake very well could wander back to the house (even if this is unlikely).

            However, most people that go through the trouble of catching and relocating a rattlesnake want a more permanent solution and are interested in moving a snake far enough that it won’t try to return. I’ve written extensively about how living with rattlesnakes is an inseparable part of living in rattlesnake country and the most ecologically-minded (and safest) plan of action when co-existing with rattlesnakes is to take appropriate precautions (like teaching children and dogs about potentially dangerous animals).  Similarly, I never advocate capturing a venomous snake because it is a dangerous activity and runs a high risk of snakebite. I’m going to assume that you know all this but, for whatever reason, you have decided it is still important to move a rattlesnake away from the house.

            To give a relocated snake the best chance of surviving, it should be moved to an area that already has a population of the same species. This is a sure-fire way of knowing that the area is appropriate and the relocated animal can fulfill all of their needs there, which include the ability to find prey, refuge, and mates. If you don’t know for sure that an area has a rattlesnake population, look for habitats that are similar to the area around your home. For Timber Rattlesnakes on the east coast, good habitats would include deciduous forests, ideally with some rocky slopes and mountains. The same is true for another venomous species that shares this habitat, the Copperhead (Agkistrodon contortrix).

            Even when a rattlesnake is moved to a perfect habitat with a resident rattlesnake population, it will still go through an adjustment period. A study conducted in the early 1990’s radio-tracked a number of Timber Rattlesnakes in Pennsylvania to compare behavioral differences between snakes that had always lived in a particular area versus snakes that had been relocated to that area (the relocated snakes had been captured from areas 5-107 miles [8-172 km] away from their new home). I’ll let the original authors (citation at the bottom of this post) describe the take-home message of the study:

Our results clearly indicate that long-distance geographic translocation (i.e., relocation) results in decreased survival and an alteration of the behavior of C. horridus. Specifically, translocated snakes made frequent and extensive movements. The pattern of movements suggested either the snakes were searching for familiar environmental features, or they were exploring the new territory in order to become familiar with the existing conditions. Translocated snakes suffered from higher rates of overwintering mortality, predation, and disease than did residents. Only four snakes out of 11 (36.7%) are known to have survived through two complete active seasons following translocation.”

            This isn’t meant to be all doom and gloom. The authors note that their relocated snakes were able to find denning sites, even if they did die over the winter in higher proportions than resident snakes. In addition, relocated snakes that did survive the first year or so or life in their new home gradually started to exhibit behavior more similar to resident animals. This means that they started to move around less, and shorter movements reduce a rattlesnake’s risk of being found and eaten by a predator (or run over by a car). The authors further note that young snakes may have an easier time adjusting to a new area than the adult snakes that they had moved around.

            A smaller-scale study conducted in South Carolina had slightly more encouraging news. Of four Timber Rattlesnakes relocated from their capture location, none tried to return to their original home and only one had died after a couple of years, when the study concluded. The animals in South Carolina may have fared relatively well because in the southeastern United States, Timber Rattlesnakes do not seem to rely as much on specific denning sites that are used year after year. This may mean southern snakes are more adaptable to changing conditions but more research with more snakes is needed before this can be said with confidence.

            On a very large scale, when confronted with news that an entire Timber Rattlesnake den was going to be destroyed by some highway development in Kansas, a dedicated group of researchers undertook an intensive effort to identify a new suitable home for the snakes that lived there. These researchers looked for new potential sites with limestone caverns (for winter refuge and denning sites) surrounded by large areas of grasslands and fields (Timber Rattlesnakes out west tend to use different habitats than on the east coast) and lots of small mammals to eat. They even made sure that there were appropriate basking areas that faced the sun in the right direction. Finally, and perhaps most importantly, the new habitat would have to be away from too many humans. They found one site that met all of their criteria and moved 29 rattlesnakes from the doomed highway den to this new site. After a couple years of monitoring, it looks like their homework paid off and the relocated rattlesnakes are generally making themselves at home.

            So, is relocating a rattlesnake away from its original habitat a death sentence? Not necessarily. By carefully choosing an appropriate and suitable relocation site, you can give a rattlesnake a reasonable chance of surviving in a new home. Even in seemingly excellent habitats though, relocated rattlesnakes often have a difficult time adjusting and experience a relatively high risk of dying from disease, predators, or exposure.


            This post is focused primarily on Timber Rattlesnakes and the habitats they use, but the same general concepts are true for all snakes. If you want to move a snake away from your home and give it a good chance of surviving, you must give a lot of thought to that snake’s needs and ensure that the new home meets these needs. If you have a snake you want to relocate and you're not sure what to do, you can ask me.

Want to Learn More? Check Out These Articles:

M. L. Walker, J. A. Dorr, R. J. Benjamin, & G. R. Pisani (2009). Successful relocation of a threatened suburban population of timber rattlesnakes (Crotalus horridus): combining snake ecology, politics, and education IRCF Reptiles and Amphibians, 16 (4), 210-221

Nowak, E.M., Hare, T, & McNally, J (2002). Management of ‘‘nuisance’’ vipers: effects of translocation on western dia- mondback rattlesnakes (Crotalus atrox). Biology of the Vipers, 533-560

J. R. Mohr (2010). Autoecology of the timber rattlesnake (Crotalus horridus) in the South Carolina mountains Dissertation, Clemson University

Reinert, H., & Rupert, R. (1999). Impacts of Translocation on Behavior and Survival of Timber Rattlesnakes, Crotalus horridus Journal of Herpetology, 33 (1) DOI: 10.2307/1565542

Sealy, J. (1997). Short-distance translocations of timber rattlesnakes in a North Carolina state park: a successful conservation and management program. Sonoran Herpetologist, 10, 94-99

Friday, November 16, 2012

Friday Roundup: Extinct, Almost Extinct, and Not Quite Extinct Anymore Edition

Grand Cayman Island Blue Iguanas Are Now Endangered...And That's Good News: A huge, bulky, and blue iguana that reaches up to five feet long can be found the Grand Cayman Islands but, for a while there it looked like it was on its way out. Because of hunting by humans, interactions with species introduced by people, roadkill, and habitat destruction, the Blue Iguana (Cyclura lewisi) almost vanished forever and was reduced to less than 25 individual animals in the wild. However, because of the work of a few conservation organizations and passionate individuals, a intensive program was initiated to protect the iguana in the wild and bolster their populations with a captive breeding program. As a result of their successful efforts, the International Union for the Conservation of Nature recently upgraded the species' status from Critically Endangered to Endangered. The Blue Iguanas are not out of the clear yet, but this is encouraging news. For more information regarding Blue Iguana and the organizations working to conserve them, check out the International Reptile Conservation Foundation and the Blue Iguana Recovery Program.

New Lizard Species Discovered! Check It Out Fast Because It's Going Extinct: This world has much more to be discovered and described. Just this year, a new species of skink, the Coastal Plains Skink (Ctenotus ora) was found south of Perth, Australia. This lizard's habitat is under siege by an incoming housing development. The animal was almost extinct before we knew it even existed. Now, the question is whether we will allow it to go extinct anyway.

A New Ferret Colony in South Dakota? The Black-footed Ferret (Mustela nigripes) was thought to be extinct in 1979 but a group of the animals was then discovered in 1981, in Wyoming. These animals became the basis for an intensive conservation. By 1987, this Wyoming population had gone extinct too, but there were now some ferrets in a captive breeding program. In 1991, biologists had started to reintroduce the species to the wild and so began a relatively successful conservation story (here's a great timeline). There was some recent excitement about three ferrets found on Standing Rock Sioux Reservation in South Dakota; you see, this was not a site where the animals had been reintroduced and there was some speculation that this was a wild and previously undiscovered population. However, I spoke with Virginia's foremost authority on the species, David Jachowski, and he informed me that federal officials suspect that these three animals have simply wandered away from the nearest reintroduction site, about 70 miles (113 km) south. Not as exciting as discovering a new population, but encouraging news that the Black-footed Ferret may be able to disperse across the landscape and be able to survive in areas in addition to the intensively managed reintroduction sites.

"A Gopher Tortoise Scampers To The Water": Bonus points for anyone that can identify what is wrong with this article

G. M. Kay, & J. Scott Keogh (2012). Molecular phylogeny and morphological revision of the Ctenotus labillardieri (Reptilia: Squamata: Scincidae) species group and a new species of immediate conservation concern in the southwestern Australian biodiversity hotspot Zootaxa, 3390, 1-18

Saturday, November 10, 2012

Friday Roundup: Mexican Amphibians and Sharks for Dinner

Trouble for the Mexican Axolotl: The Axolotl is a large aquatic salamander (similar to the mudpuppy we have in the States) and a fascinating creature that defies the typical amphibian life never leaves the water and remains looking like a juvenile animal. Its native range includes much of what is now Mexico City and, as you might expect, its aquatic habitats are heavily polluted. A summary of the Axolotl's precarious position.

Study Shark Eaten: Radio-telemetry and satellite technology have revealed some extraordinary aspects of animal ecology, informing us of wildlife behavior and movements. Often, researchers are able to learn about common predators too...many of the snakes I've radio-tracked were eaten by hawks, for example.  Shark researchers in South Africa recently had a similar revelation, when a tagged White Shark was found to have been killed and eaten by people in nearby Mozambique. The organization sponsoring this research, OCEARCH, does fascinating work on large sea creatures. Check out their site to keep track of a number of sharks that are still swimming around.

Speaking of Study Animals Being Captured: From our neck of the woods, a catfish angler landed some huge bycatch in the Tallapoosa River in Alabama, an 83 lb (38 kg) Alligator Snapping Turtle. Turns out that this turtle had been captured and tagged eight years earlier by amateur body-builder and freelance beard model Jim Godwin when he was studying the species for the Alabama Natural Heritage Program. Instead of becoming soup (the species is protected), the turtle was released back into the river. Although the article mentions that the Alligator Snapping Turtle is the largest species of freshwater turtle, that's only true in North America...there are softshell turtles in Asia that likely take the crown as the world's biggest.

Octopus Killed in Washington Sparks Outrage: A diver legally killed a Giant Pacific Octopus in a popular diving spot. These huge animals (at reaching over 150 lbs <70 kg="kg">, they are the largest species of octopus) are intelligent and beautiful, at least to divers frequent the area (check out this picture if you don't believe me), and the event created a lot of controversy. This editorial emphasizes some of the positive outcomes and lessons learned: the diver that killed the animal is now advocating for regulations forbidding future killings of octopus at the site.

The Rarer Your Species Becomes, the More You're Worth: A summary from NPR about the economics of rare species. As collecting and poaching get out of control, the desired species becomes rarer and rarer. Because these species become rarer to find, the cost for that species increases. That only increases the incentive to capture the few remaining individuals.

Dirk Stevenson, the Barbara Walters of Herpetology: Dirk Stevenson, who once helped me not find Indigo Snakes in Florida, spends a day in the field with herpetologist and professor Carlos Camp and relates the experience on his blog, The Naturalist.

Rarely Observed Animal Washes Up On New Zealand Shore: There is still so much we don't know about the natural world. A couple years ago, two animals washed up on a New Zealand beach and this event represented the first time scientists were able to see their species (they had only been known from three partial skulls). They were whales.

Crocodile Skin is Sensitive Too: Most people probably don't think of the rough and scaly skin of a crocodile as being sensitive, but perhaps they should. On Croc Blog, Adam Britton summarizes a recent study suggesting crocodile skin is more sensitive than our fingertips.

I Need To Get Some of These: Setting up traps to take a picture or record video when an animal walks by is a great way to learn what creatures are prowling around, especially when those animals are secretive or elusive. Here's a Townsend's Big-eared Bat from Nature of a Man and some weasels from Camera Trap Codger and TrailBlazer.

Artificial Rivers in Zoos May Lead to More Hellbenders in Missouri: A story about some recent successes breeding Hellbenders for eventual release in the wild.

Ever Wonder Why You've Never Seen a Snake Eat Fruit? Wonder no more, thanks to Andrew Durso at Life is Short, but Snakes are Long.

Don't Do This: Competitive eating is one thing, competitive eating of insects and worms is another. A participant dies after competing in (and winning) a contest to win a pet snake. I do, however, recommend eating grasshoppers in moderation.