HOW DO PREDATORS LOCATE NESTS OF ORNATE BOX TURTLES (TERRAPENE ORNATA)? A FIELD EXPERIMENT

Turtles are subject to high rates of nest destruction from mesopredators. Scents associated with nest contents, proximity to woody edge, and marker flags are suggested cues influencing nest predation. With few exceptions, most turtle nest predation studies involve aquatic turtles. During studies of terrestrial Ornate Box Turtles (Terrapene ornata), we documented high rates of nest predation. We designed an experiment to simultaneously compare combinations of factors which may influence predation using artificial nests on two sand prairies used for nesting. Artificial nests contained treatments arranged in 1 1 m2 plots: disturbed soil with a buried Chicken (Gallus gallus) egg marked with a flag; disturbed soil without an egg, but marked with a flag; disturbed soil with a buried egg and no flag; and undisturbed soil marked with a flag. We established replicate transects of arrays perpendicular to the woody edge of the prairie and observed excavation for 24 d each in June, July, and August. Disturbed soil was the only significant predictor of excavation. With the exception of the undisturbed soil with flag, effectively untouched by predators for 22-24 d, average nest survival was low (range: 2-3 d). There were no significant differences in destruction of artificial nests between distances from the woody edge and artificial nests. Because undisturbed soil did not elicit digging, we suggest that nesting in soft sandy soil is not only adaptive because of ease of excavation, but rain and wind also hide surface evidence and/or odor of digging quickly and, therefore, obscure the nest.