The Effects of Temperature on the Turnover of δ18O and δD in Juvenile Corn Snakes (Elaphe guttata): A Novel Study with Ecological Implications

Samuel Hirt,Kent Hatch

doi:10.3390/d11020019

Abstract

The use of natural variation in stable isotope ratios continues to be used in ecological studies without proper validation through laboratory studies. This study tested the effects of temperature, time, and turnover in the scales of juvenile corn snakes (Elaphe guttata) in a controlled, laboratory environment. Snakes were assigned to four treatment groups (24 °C, 27 °C, 30 °C, and freely thermoregulating), and one snake from each group was sacrificed weekly. Scales from each snake were washed, dried, and analyzed for δD and δ18O at the Stable Isotope Research Facility for Environmental Research at the University of Utah. The effects of temperature on the turnover of tissues was only significant when comparing the thermoregulating group to the pooled treatment groups (24 °C, 27 °C, and 30 °C) in the δ18O of scales (p = 0.006). After normalizing data on the δD and δ18O using percent change for comparison, δ18O appeared to be turning over at a faster rate than δD as indicated by an analysis of covariance (ANCOVA) test for homogeneity of slopes (F1,53 = 69.7, p < 0.001). With further testing of assumptions, a modification of our methods could provide information on the composition of drinking water sources in a species that switches between two isotopically distinct sources, such as during seasonal shifts in habitat or migration, and/or estimates of long-term field metabolic rates based on the turnover of these isotopes.

Highlights

Stable isotopes are useful as natural, biological indicators, providing ecological data such as patterns of migration, nutrition, and trophic position [1,2]
Oxygen and hydrogen isotopes are underutilized in ecological studies of ectotherms, partly
Oxygen and hydrogen isotopes are underutilized in ecological studies of ectotherms, partly because of the paucity of controlled laboratory experiments needed to effectively interpret data because of the paucity of controlled laboratory experiments needed to effectively interpret data gathered the field

Summary

Introduction

Stable isotopes are useful as natural, biological indicators, providing ecological data such as patterns of migration, nutrition, and trophic position [1,2]. The observance of naturally occurring variations in stable isotopes continually provides application in clinical [3], forensic [4,5], and ecological fields of study, especially among mammals and birds [6,7,8,9]. The significance and the interpretation of isotopic data need validation by controlled, laboratory experiments before application in ecological studies. Despite arguments that validation research should be done before application in the field, there continues to be a lack of studies providing these important background data [10,12,13,14]. We provide results from controlled laboratory experiments that can provide information for the interpretation of future field experiments, especially with terrestrial ectothermic vertebrates

Methods

Results

Conclusion