Nonlinear phenomena in the natural howling of a dog-wolf mix

It was reported to the first author that a female dog-wolf mix showed anoma lously rough-sounding vocalization. Spectral analysis of recordings of the vocalization revealed frequency occurrences of subharmonics, biphonation (t wo independent pitches) and chaos. Since these nonlinear phenomena are curr ently widely discussed as integral to mammalian vocalization [Wilden et al. , Bioacoustics 9, 171-196 (1988)] or as indicators of vocal pathologies [He rzel ct al., J. Speech Hearing Res. 37, 1008-1019 (1994); Riede ct al., Z. Sgtkde 62 Suppl: 198-203 (1997)], we sought to understand the production me chanism of the observed vocal instabilities. First the frequency of nonline ar phenomena in the calls was determined for the female and four additional individuals. It turned out that these phenomena appear, but much less freq uently in the repertoire of the four other animals. The larynges of the fem ale and two other individuals were dissected post mortem. There was no appa rent asymmetry of the vocal folds but a slight asymmetry of the arytenoid c artilages. The most pronounced difference, however, was an upward extension of both vocal folds of the female. This feature is reminiscent of "vocal l ips" (syn. "vocal membranes") in some primates and bats. Spectral analysis of the female's voice showed clear similarities with an intensively studied voice of a human who produces biphonation intentionally. Finally, the poss ible communicative relevance of nonlinear phenomena is discussed. (C) 2000 Acoustical Society of America. [S0001-4966(00)00510-5].