Ylenia Chiari and Scott Glaberman
University of South Alabama, Dept. Of Biology, 36688 Mobile, AL, USA
Global climate change is one of the factors negatively affecting natural biological systems and current predictions highlight how rises in environmental temperature could lead to large-scale biodiversity loss. In order to assess the implications of environmental temperature changes on organisms, it is critical to understand how changes in temperature affect the ecology and physiology of different species.
In fact, changes in environmental temperature do not affect species equally as ectothermic species are more highly dependent on external temperature and therefore are more likely be sensitive to temperature changes.
Turtles are ectotherms since their internal body temperature depends on external heat sources (i.e. environment). In turtles, metabolism, morphology, sex-determination, activity patterns and other physiological and ecological characteristics are often temperature-dependent, making them especially sensitive to climate change. Very little is known about the potential effect of temperature variation on behaviour and ecology of turtles, especially across different species. Such information would offer an important early warning of which turtle species could suffer the most from future temperature changes and help define conservation measures to protect these sensitive species. Furthermore, in addition to climate change, understanding the influence of external temperature on turtle biology can help determine how suitable current captivity conditions are for different species, which is critical for designing successful exsitu management programmes.
We obtained funding from the BCG to carry out a study on thermal behavior of nine different species of aquatic and terrestrial turtles under captive conditions. The data collection phase of the study was completed in the summer of 2014. Information collected included how much time an individual spent at a certain temperature and which temperatures were selected most often. The turtles were studied at the “A Cupulatta” turtle centre in Corsica, France (www.acupulatta.com). One benefit of studying many species under similar captive conditions is that it enables assessment of temperature-related behavior of many different turtle species under similar environmental temperature ranges, yielding data that is truly comparative (Figure 1). For each species, we sampled a total of 10 individuals, equally distributed between females and males, when possible. The use of more than one individual per species provides information on individual variation in temperature-related behaviour and body condition (mass, body conditions).
Figure 1. Chelonoidis sp. in an internal enclosure at the centre “A Cupulatta” in Corsica (France).
In order to evaluate the environmental temperature selected by the turtles, a datalogger (i-button ®) was attached to the carapace of each individual (Figure 2), and the temperature was measured every 20 minutes from July 1st to the end of October 2014. Data-loggers were attached to the shell by using epoxy material commonly used for surfboard repair. This material does not influence the temperature reading, ensures protection of the data-logger from sun and water exposure, and can be removed from the shell of the animals without damaging it. Additional dataloggers were placed in external and internal turtle enclosures to record ambient temperatures in different environments (e.g., full sun exposure, shade, internal enclosure), which provides data on the range of temperatures available to the animals. Also, because temperatures preferred by animals have been shown to be associated, in part, to body mass and shape in other organisms, we collected basic morphological measurements of each individual in which temperature was also tracked. After the recording period, the data-loggers were removed and we have just started organizing the data for analysis. One of the benefits to having thousands of temperature data points for many individuals and species is that it provides very rich information on variation in thermal behaviour; yet, it also requires developing creative approaches to harness this information and distil it in ways that help us understand the major patterns and implications for how temperature influences the biology of turtles.
Figure 2. Three individuals of Indotestudo elongata each with a data-logger attached on the carapace
We would like to thank our collaborators, Dr Pierre Moisson and Dr Miguel Carretero. We would also like to thank the staff of “A Cupulatta” turtle centre, where the data have been collected, and especially Maryline Moreau, Paola Houbrix, and Jean-Sebastien Tafani. We are grateful to the British Chelonia Group for funding to support this work.