Body Size and Digestive Efficiency in a Herbivorous Freshwater Turtle: Advantages of Small Bite Size

In reptiles, large body size has been considered a great-if not essential-asset for herbivory. However, in a herbivorous freshwater turtle, Pseudemys nelsoni, 12-g hatchlings had significantly better digestive performance than did 3,000-g adults. On a diet of duckweed (Spirodela polyrhiza), hatchlings processed nearly four times as much food on a mass-specific basis than did adults while maintaining equivalent digestibilities as adults. Hatchlings gained more than four times the amount of energy and nitrogen daily on a mass-specific basis that adults gained. On a diet of hydrilla (Hydrilla verticillata), hatchlings fed selectively, ingesting a diet significantly higher in energy and nitrogen and significantly lower in lignin than the diet of adults. Small bite size of small herbivorous reptiles is a mechanism that enables them to meet higher mass-specific nutrient requirements by improving both the physical structure and-through selective feeding-the nutrient quality of the diet.