From Acta Herpetologica.
While most species of turtle exhibit secondary sexual dimorphisms that can be used to reliably infer sex, there are some species that are very difficult to sex Ö Therefore, we tested the novel method of using a vibrator to sex turtles by stimulating male turtles to evert their penises. Once a male turtle was captured, we attempted to lnduce an erection by applying an 18 cm, variable-speed, silver bullet vibrator to its shell and tail Ö
In general, turtles appeared to respond best when only the tip of the vibrator was touching them and when the vibrator had fresh batteries and was set on the fastest setting. Also, they seemed to respond best when the tip was held firmly against them (rather than allowing it to bounce), but not be pressed hard against them. Both allowing it to bounce and pressing it too hard generally resulted in turtles holding their limbs and tail tightly against the body, rather than relaxing. Additionally, it was often useful to move the vibrator around in small, slow, steady circles.