Cloacal Popping in Snakes

Abstract

-Tactile stimulation to the Sonoran coral snake (Micruroides euryxanthus) and the western hook-nosed snake (Gyalopion canum) induces an expulsion of air from the cloacal vent which results in an audible popping sound. The behavioral context of cloacal popping differs in these two species, as does the acoustics of the popping sound. The cloacal pops produced by M. euryxanthus are rather consistent and show a low amplitude (50-53.5 dB), limited frequency range (442-5523 Hz), distinct temporal patterning, and harmonics. The cloacal pops released by G. canum are more variable; the initial pops are of high amplitude (70-73 dB) and broad frequency range (359-15,178 Hz), but in subsequent pops the amplitude falls off and the frequency range narrows; no temporal patterning or harmonics were observed. Cloacal popping is driven primarily by the M. Sphincter cloacae but may involve other extrinsic cloacal musculature. The presence of this unusual defensive sound in only these two sympatric snakes suggests its function against a common