PARENT SESSION
Oral Session # 58: Rare, Threatened, and Endangered Species III: Reptiles and Amphibians.
Presiding: K Beard
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 202.

¹⁵N enrichment of lizard uric acid: Can ¹⁵N be used as a measure of body condition in the wild?

Hatch, Kent^*,1, Makin, Jessica¹, ¹ Brigham Young University, Provo, UT, USA

ABSTRACT- Stable isotopes are used by animal physiological ecologists to determine such things as dietary sources, migration, and trophic levels. Attempts have been made to use ¹⁵N values as indicators of body condition as well. The assumption is that proteins are ¹⁵N enriched during anabolism whereas nitrogenous wastes are ¹⁵N depleted relative to diet. Catabolism then only further enriches the tissues as ¹⁵N depleted urates are excreted. However, this model is based, in part, on only a single study of 8 cattle demonstrating ¹⁵N depletion of urea relative to diet. Because of their small size and ease with which uric acid can be collected, lizards are a logical system to use to test the hypothesis that, across taxa, nitrogenous wastes are ¹⁵N depleted relative to diet. Based on a study of twenty side-blotched lizards, we show that nitrogenous wastes are ¹⁵N depleted across taxa. We evaluate the usefulness of this method for determining body condition on the wild.

Key words: body condition, lizards, stable isotopes, catabolism