Bone conduction hearing in turtles.

Audiofrequencies were delivered to specimens of 3 turtle families by ac and bc in an attempt to elicit a behavioral response. Aerial signals with intensities up to 100 db SPL failed to elicit any consistent response. The same signals delivered directly to the carapace resulted in brisk head withdrawals. There was little energy loss measured along the shell suggesting it may serve in a minor role as an acoustic receptor. Turtles could use bc hearing in short distance detection even when withdrawn into the shell. Although the ear is likely mediating the head reflex, somatic mechanoreceptors cannot be completely excluded.