Abstract

Hatchling orientation has been widely studied among marine turtle species, but much less so in nonmarine turtles. Yellow mud turtles (Kinosternon flavescens) exhibit an unusual semiaquatic life history with terrestrial estivation or hibernation in summer through winter and aquatic mating and feeding in spring and early summer. Hence, these turtles migrate between wetlands and uplands at least twice each year along the same migration path. To understand the orientation methods used by juvenile turtles, hatchling and second-year mud turtles emerging from hibernation were captured before reaching the water and released in one of two circular arenas placed out of sight of and on the opposite side of the wetland. Recapture locations of these turtles along the perimeter of the arenas suggested that hatchlings probably used visual (e.g., polarized light) or perhaps olfactory cues to orient toward water. However, second-year turtles maintained the same compass bearing used prior to initial capture, suggesting that they employed an internal compass mechanism that was not overridden by proximate cues from the wetland. The probable mechanism for setting that course was likely a sun and/or a magnetic compass.

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