Peter M. Narins
Dept. of Biol., UCLA, 405 Hilgard Ave., Los Angeles, CA 90024
The white-lipped frog, Leptodactylus albilabris, exhibits the greatest sensitivity to substrate-borne vibrations (seismic stimuli) reported to date for any terrestrial animal. Nerve fibers from the sacculus, the source of this extraordinary sensitivity, show clear responses to sinusoidal seismic stimuli with peak accelerations less than 0.001 cm/s[sup 2]. In addition, this animal generates substrate-borne vibrational signals during calling. As the male's vocal sac expands, it strikes the substrate impulsively, generating a vertically polarized surface (Rayleigh) wave that is detected by neighboring males. These Rayleigh waves are used as intraspecific communication signals to coordinate chorus behavior in this species. Recently, a particularly unusual behavior has been described for one species of Malaysian treefrog (Polypedates). During nocturnal courtship, females living in dense mats of floating vegetation perch conspicuously on a reed or blade of grass and tap their rear toes rhythmically. Males on neighboring reeds were observed to quickly locate and mate with the tapping female. Thus it is likely that toe tapping functions as a vibrational signal indicating the female's presence to neighboring males. It is becoming clear that seismic communication and sensitivity to whole-body vibrations are more ubiquitous among the vertebrates than had been previously imagined. [Work supported by NIH.]