Meeting Abstract
55.6 Saturday, Jan. 5 Tracking the Dietary History of Chelonians via Stable Isotope Analyses MURRAY, I.W.*; WOLF, B.O.; Univ. of New Mexico, Albuquerque; Univ. of New Mexico, Albuquerque imurray@unm.edu
We used stable isotope analysis of individual growth rings in the scutes of turtles and tortoises to gather information on their nutritional ecology. Over the course of their lives, many turtles and most tortoises accrue visibly distinct growth rings, or annuli, on the keratinous scutes that serve as a protective cover for their bony carapace. Keratin is an inert tissue and its isotopic composition probably reflects that of the animal�s diet when it was laid down. As a consequence, a series of growth rings has the potential to provide insight into the dietary history of an individual chelonian over a long period of time. Plant δ13C varies with photosynthetic pathway. This allows the plant functional group (C4 grasses and cacti versus C3 annuals) used as a nutrient source to be characterized. In addition, δ15N enriches with trophic level and thus provides insight into trophic shifts. We extracted keratin from individual annuli, and measured the δ13C and δ15N values of individual rings in juvenile to adult western box turtles, Terrapene ornata luteola, and desert tortoises, Gopherus agassizii, over a wide geographic area. Our data for box turtles shows periodic shifts from annual plants to grasses or cacti as well as shifts in trophic level. Data for desert tortoises shows significant shifts in diet from C3 annual or perennial plants to cacti or C4 plants.
