Eastern Box Turtles (Terrapene carolina, EBT) occur in mesic forests throughout the eastern United States. While previously common, both population sizes and densities are decreasing, populations are highly prone to fragmentation by roads, urbanization, and collection for the pet trade. Individuals are vulnerable to road injuries. EBT are generalist omnivores, and important seed and fungal spore dispersers. Their diets have been explored via fecal analyses, gut content analyses, and numerous anecdotal observations, showing that EBT feed opportunistically on seasonally available fruit, many other plants, invertebrates, and occasionally carrion. These studies may have underrepresented soft-bodied invertebrates, such as slugs and earthworms, in their estimates, due to their high digestibility.
We radio-located EBT in the Pine Barrens of central Long Island, New York and collected fecal and blood samples. We examined fecal samples under a dissecting microscope and identified prey items to the highest possible taxonomic level. Seeds were also quantified. Plasma was separated from red blood cells, lyophilized, and then analyzed for stable C and N isotopes ratios (δ C and δ N) indicating nutrients assimilated.
Results/Conclusions
As expected, we found highly seasonal patterns in fruit seed abundances in fecal samples correlated with fruit availability. Vaccinium fruit were found in 50% (June), 50% (July), and 20% (August) of samples, showing that EBT consumed Vaccinium fruit before they ripened and after they fell to the ground. We found Rubus and Gaylusaccia in July and August samples, and Vitis seeds in 40% (August) and 30% (October) of samples. Unidentifiable plant material were in 90-100% of samples in all periods. Coleopterans were in 70% (June), 85% (July), 80% (August), and 80% (October) of samples. Snails were in 10% of samples from June, August, and October, but in 28% of July samples. Mushrooms were in 10% of June samples, 45% (July), 10% (August), and none in October. Caterpillars were only found in June (20% of samples) and July (45%).
Surprisingly, stable isotope analysis indicated no significant differences in the δ C and δ N from EBT plasma sampled throughout their active season despite seasonal consumption patterns. Low plant digestibility reducing nutrient assimilation, diet items with similar δ C and δ N contributions, and a short study period may have affected EBT nutrient assimilation patterns.