Mechanics of sound production in toads of the genus Bufo: passive elements.

The vibration mechanics of the vocal tracts of over 40 species of toads (genus Bufo) were studied, using an apparatus to artificially activate the larynges of freshly killed animals. The effects of laryngeal ablations on the mating and release calls were studied. They confirmed the results obtained by artificial activation. The mating and release call dominant frequencies are determined primarily by the fundamental frequencies of vibration of the paired vocal cords. Vocal cord resonant frequencies are in turn largely determined by the activation air pressure and the masses of cartilagenous deposits in their lateral portions. In most species, fleshy folds within the larynx at the anterior extremities of the arytenoid cartilages cause these cartilages to vibrate during sound production, amplitude modulating the vocal cord output. In most species, the contraction pattern of the vocal musculature is reflected as a periodic pulsation. Frequency modulations of the mating call dominant (or carrier) frequency are described, partially explained, and deemphasized in importance with respect to toad acoustical communication. The findings of this investigation are made relevant to the overall problem of the structure and evolution of toad acoustical communication by use of an analogy with standard AM radio broadcast.

[1]  A. B. Wood,et al.  A textbook of sound , 1930 .

[2]  R. R. Capranica,et al.  The evoked vocal response of the bullfrog , 1965 .

[3]  The electrical response of the auditory mechanism in the bullfrog (Rana catesbeiana). , 1959, Journal of comparative and physiological psychology.

[4]  Lawrence E. Kinsler,et al.  Fundamentals of acoustics , 1950 .

[5]  Robert R. Capranica,et al.  Vocal Response of the Bullfrog to Natural and Synthetic Mating Calls , 1966 .

[6]  W. F. Blair,et al.  Mating Call in the Speciation of Anuran Amphibians , 1958, The American Naturalist.

[7]  C. Daniel Geisler,et al.  Peripheral Origin of Auditory Responses Recorded from the Eighth Nerve of the Bullfrog , 1966 .

[8]  M. Sachs.  Responses to Acoustic Stimuli from Single Units in the Eighth Nerve of the Green Frog , 1964 .

[9]  Byron Goodman,et al.  The radio Amateur's handbook , 1965 .

[10]  C. M. Bogert.  The influence of sound on the behavior of amphibians and reptiles. , 1962 .

[11]  W. H. Mcalister,et al.  The Mechanics of Sound Production in North American Bufo , 1961 .

[12]  R. Zweifel.  Effects of Temperature, Body Size, and Hybridization on Mating Calls of Toads, Bufo a. americanus and Bufo woodhousii fowleri , 1968 .

[13]  L. S. Frishkopf,et al.  Responses of Auditory Units in the Medulla of the Cricket Frog , 1966 .

[14]  Lawrence S. Frishkopf,et al.  Responses to Acoustic Stimuli from Single Units in the Eighth Nerve of the Bullfrog , 1963 .

[15]  William A. Watkins,et al.  The harmonic interval : fact or artifact in spectral analysis of pulse trains , 1968 .

[16]  R. Schmidt.  HEARING AND RESPONSES TO CALLS IN ANURANS , 1964 .

[17]  K. R. Porter.  Morphological and Mating Call Comparisons in the Bufo valliceps Complex , 1964 .

[18]  W. F. Blair.  Call difference as an isolation mechanism in Southwestern toads genus Bufo , 1956 .