Monday, May 19, 2014

Turtle Activity: Living the Life in the Sun –-Guest Post–-


    Hello, our names are Sara Bresse and Nadeen Masarweh, and we are 5th year biology students at San Diego State University in California. This is our first time writing a blog post, and as a research assignment for our experimental ecology course, we observed turtle activity at our turtle pond on campus. Throughout the course of this semester we have conducted a few ecological class research projects. Our final assignment was to conduct our very own independent project, and we decided to write a guest blog post as an outreach tool and to inform others of our exciting results. Our focus was strictly observational and there were no manipulations made while collecting our data.

    We all love taking a vacation, and most of us would prefer to take a beautiful vacation at a sunny, hot beach. This is because a lot of people enjoy sunbathing and swimming on their vacations. Most of us only get to enjoy this kind of lifestyle during vacations for about a week or two, but lucky pond turtles, such as Trachemys scripta elegans, get to live the extravagant life every day (at least here in sunny San Diego, California).

    Pond turtles spend most of their time basking (laying out in the sun next to a body of water). This is because unlike humans, reptiles such as turtles are ectotherms (formerly known as “cold blooded”) and require the sun to increase their body temperature. Mammals, such as humans, are endothermic (aka warm blooded), and do not rely on the sun (or external heat sources) to maintain a functional internal body temperature. 

    Turtles bask daily to maintain a preferred body temperature between 30° to 36°C so that they can perform normal physiological functions (86° to 96.8°F, Boyer 1965). They also can swim in the pond water to avoid deviating from their preferred body temperatures (Boyer 1965). Turtles engage in this activity because the pond water is typically at a lower temperature than the environmental temperature, thus lowering their overall body temperature. 

    Temperature also plays a critical role in turtle reproduction. Turtle eggs require a certain temperature for successful development. If an increase in global temperature were to occur, there could be an increase in turtle egg fatality and an alteration in sex ratios (Poloczanska 2009).

    Pond turtles prefer to haul out on objects such as rocks and logs that are on or next to their pond so they can easily escape into the water if necessary (Boyer 1965). This is a great defense mechanism used by pond turtles that feel threatened, but because our pond turtles at the San Diego State Koi Pond have more interaction with humans, most of them tend to tough it out like the Teenage Mutant Ninja Turtles and remain basking instead of fleeing into the water when approached. 

     After observing the turtles for a week at SDSU, we found a significant relationship between temperature, weather, and turtle activity. Through analyses we established that weather (i.e., cloudy or sunny) is more significant than temperature in determining the type of activity the turtles are engaged in. More turtles seemed to be bathe during the cloudy weather, because we found the temperature to be warmer on those days. This could be because clouds serve as an insulator, keeping the warm air inside the atmosphere. On the other hand, we noted that on sunny days, the temperature was not as high and turtles were found more often to be basking on the rocks near the pond. Clear sunny days were cooler because the sunlight and energy that would typically make environmental temperatures increase could be released back into the atmosphere and are not guarded by the clouds. 

    Highest turtle activity occurred between the temperatures of 24° and 29°C (75-85°F) . There was a mixture of turtles basking and bathing during these temperatures and there was no relation found between temperature and whether they were basking or bathing. We believe that if we had a greater sample size we would have found significance in basking or bathing with an increase or decrease in temperatures. There was minimal turtle activity found below 75°F and above 85°F. 

    After observing the turtles between the hours of 7am-11pm, we found high activity of basking and bathing between the hours of 9am-4pm and no turtles were visible around the pond outside of those hours. We also noted that the highest percent of turtles found bathing and basking around the pond occurred around 1pm, probably due to high sun exposure and temperature during this time.

    This concludes our overall findings of our project and we hope that you enjoyed reading our post! We are glad to contribute to the ecological community and we hope to have broadened your interest in pond turtles.

Want to Learn More?

Boyer, D. (1965). Ecology of the Basking Habit in Turtles Ecology, 46 (1/2) DOI: 10.2307/1935262

Poloczanska, E.S., C.J. Limpus, and G.C. Hays. 2009. Chapter 2. Vulnerability of marine turtles to climate change. Advanced Marine Biology 56:151-211.

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