Monday, January 16, 2012

Trapping Tropical Turtles Today

            Some animals, like turtles, can live for decades. But most turtle studies only last a few years (one big reason is that many studies are conducted by graduate students and, contrary to popular belief, students do in fact want to graduate quickly). So, because turtles live for decades and most studies are completed after just a couple years, that means that much of what we know about these animals is based on snapshots in time.

            Since many of us want to know best how to conserve turtle populations, it is important that we have a better understanding about how they change over time. Knowing how populations naturally fluctuate allows us to better understand how they might respond to conservation threats. Establishing this baseline data is particularly important for undisturbed populations.

People have been trapping turtles in this swamp for 20 years
            When I heard that researchers and students had been trapping, on and off since 1991, a population of White-lipped Mud Turtles, Kinosternon leucostomum, in a Costa Rica swamp surrounded by old-growth rainforest, I realized that this population represented a unique opportunity. By continuing the trapping myself, and then compiling and examining the data collected by many different people over the last two decades, it would be possible to see how a turtle population has changed over time. And I wouldn't need to conduct a 20-year field study to do it.

            So, thanks to the Organization for Tropical Studies, I find myself back at La Selva. I arrived yesterday and will be here, walking amongst the peccaries and listening to the toucans, on and off until April.

            Today, the first task was to find the swamp (those familiar with La Selva may know this small forested pond as the Research Swamp). Unlike my previous research here, this work is to take place during the day; I was pleasantly surprised to find that the path to the swamp was well-marked with flagging and easy to follow (when it is light out).

            Deep in thought, I stumbled into a herd of collared peccaries, they let me know I was too close by snapping their teeth together; doing so produces a sound meant to warn off potential predators. Collared peccaries are generally thought of as relatively harmless creatures, but I give them my respect. You don’t last long in tropical forests filled with pumas, jaguars, and venomous snakes by being a pushover.

            Speaking of venomous snakes, there is no shortage of them here. Perhaps the most infamous is the Fer-de-lance, also known as the Terciopelo, Bothrops asper. These large vipers are most often observed at night, perhaps as they travel across a path or when they are coiled up in an ambush position along a tree trunk, waiting for a rodent or frog to scurry by. Swampy areas are thought to be the preferred habitat of the Terciopelo, so I reminded myself to watch my step when I was mucking through the mud to set my turtle traps. It was good advice.

Notice the trap in the waterway
            The water level was relatively low, so it was somewhat of a challenge to find areas deep enough to cover the bait containers within the traps. It is important to have the bait underwater so that the scent (in this case, of sardines in tomato sauce) can easily reach any hungry turtles.

            Another important thing to consider when trapping turtles, or any wildlife for that matter, is to make it easy for the animal to encounter the trap. Although the bait might entice a turtle to crawl over somewhere where it might not go otherwise, you will probably have better luck putting the traps where the turtles are going anyway. So, with this in mind, I tried to put the traps in areas where small streams ran through the vegetation, I figured these pathways would be how the turtles got around.

My initial view of the Terciopelo
            As I stumbled through the mud and stepped over large tree roots and downed logs, I caught the familiar shape of a coiled snake. Basking in the sunlight sat the infamous Terciopelo, a relatively small one. If it noticed me as well, there was no indication. I couldn’t help but think about what kind of animal was, for lack of a better word, confident enough to sit on a log where other predatory animals might easily see it. I did not need anyone to tell me not to get too close.

            If you read this blog, then you know that I am fond of snakes and I do not fear them. I know that snakes do not represent much of a danger to me because I take a few small precautions (like wearing boots instead of sandals). However, even though I knew there were Terciopelos around me all along, I couldn’t help but start overreacting a bit whenever a branch scraped across my back. I also noticed my steps became a little slower and more deliberate. In any case, if I walked by any more snakes, I did not see them.

A closer look
            But, we are here to talk about trapping turtles. I am most interested in White-lipped Mud Turtles; I hope some wander into the traps tonight. Of course, there are many animals that like to eat sardines, so we will have to see what shows up tomorrow morning.

A White-lipped Mud Turtle I noticed at a
nearby swamp  a couple years ago




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Much of what I write is based on my experience in the field, however, I also rely on the research of others. Citations to relevant articles are provided below.

Wasko, D., & Sasa, M. (2010). Habitat Selection of the Terciopelo (Serpentes: Viperidae: Bothrops asper) in a Lowland Rainforest in Costa Rica Herpetologica, 66 (2), 148-158 DOI: 10.1655/08-064R2.1

CONGDON, J., DUNHAM, A., & VAN LOBEN SELS, R. (1993). Delayed Sexual Maturity and Demographics of Blanding's Turtles (Emydoidea blandingii): Implications for Conservation and Management of Long-Lived Organisms Conservation Biology, 7 (4), 826-833 DOI: 10.1046/j.1523-1739.1993.740826.x

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