The Herpetological Journal

pp.89-94

Authors: Bruce A. Young, Jackie Solomon And G Eorg E Abishahin

Abstract: As part of its defensive display the Indian rat snake, Ptyas mucosus, mediolaterally compresses the anterior portion of its body and expands its throat region ventrally. During this postural display P. mucosus produces a deep, rumbling defensive growl. Acoustic analysis of this growl revealed it to be a long moderately loud sound dominated by lower frequencies. Binding the neck and anterior portion of the body with surgical tape prevented the postural display; while the defensive sounds produced by bound specimens had the same duration and amplitude, their frequency increased significantly. The tracheal membrane of P. mucosus is unusually wide and expands away from the tracheal rings into the body cavity. We hypothesize that during the defensive postural display the expansive tracheal membrane is collapsed forming isolated pockets which have a resonance effect on the exhalent airstream. Ptyas mucosus may be an acoustic Batesian mimic of the king cobra, Ophiophagus hannah.

Keywords: sound production, acoustics, Batesian mimicry, colubrids, defensive behaviour