Growth Rate and Duration of Growth in the Adult Canine of Smilodon gracilis and Inferences on Diet Through Stable Isotope Analysis

Abstract

Trophic structure and interconnectedness have important implications for diversity and stability in ecosystems. While it is generally difficult to determine trophic structure and the specific prey of predators in ancient ecosystems, analysis of stable isotope ratios in tooth enamel can be used to exclude taxa from a predator’s diet. This study analyzes δ¹³C_v-pdb and δ¹⁸O_v-pdb values in a canine of Smilodon gracilis to understand tooth growth and the preferred prey of this species. Oxygen isotope results show a 5 mm/month growth rate and a duration of growth estimated to be 16 months long. The carbon isotope results suggest consumption of animals that depended only on C₃ plants. Due to overlap in δ¹³C_v-pdb values, it appears that Hemiauchenia and Platygonus may have been included in the diet of this individual of S. gracilis, while Equus and Mammuthus were probably excluded. Also, the mean δ¹³C_v-pdb values of S. gracilis were more negative than the prey, which may indicate prey captured in a closed environment, or consumption of species present at Leisey 1A but not yet analyzed isotopically. This study shows that determining trophic relationships and interconnectedness within ancient ecosystems is possible.