Acoustic Features of the Weeping Lizard's Distress Call
The study of acoustic communication in lizards has been restricted and mainly focused on Gekkota. The rest of the lizards, Unidentata, are generally considered voiceless, although there are sparse reports on vocal sound production in members of different families. We analyzed the spectro-temporal characteristics of the distress calls emitted by the Unidentata lizard, Liolaemus chiliensis (the weeping lizard; Liolaemidae), the only species of this highly diverse genus (>220 species) that vocalizes. We also explored the relationships of the call characteristics with the sex and size of the individuals. The vocalizations of L. chiliensis are highly diverse and complex compared to any known call produced by Unidentata lizards. They exhibit pronounced frequency modulations, various nonlinear phenomena, and harmonics that extend into the ultrasonic range. Fundamental frequency and call duration are correlated with body size, and males emit louder but simpler calls (i.e., with less nonlinear phenomena) than females. Based on the characteristics of the vocalizations, we discuss their potential role for startling predators and/or alerting conspecifics to predation risk.
(A) Oscillogram and (B) spectrogram of a representative distress call of a female of Liolaemus chiliensis (snout–vent length = 99.8 mm), showing harmonics extending into the ultrasound range (>20 kHz), a limit indicated by the dotted line. Recording made with the G.R.A.S. 40BE microphone.
Relationships between body size and (A) dominant and fundamental frequency and (B) duration of the distress call of Liolaemus chiliensis.
Spectrograms of the five categories of simple distress calls of Liolaemus chiliensis, according to the pattern of frequency modulation: (A) invariant, (B) upward, (C) downward, (D) bell-shaped, and (E) U-shaped. Note that the downward and bell-shaped patterns have harmonics that occur at frequencies higher than 20 kHz. Recordings made with the Sennheiser ME 66 microphone.
Spectrograms of the four categories of complex frequency-modulated patterns of distress calls of Liolaemus chiliensis. (A) Subharmonic. The arrow shows one of the subharmonics. (B) Deterministic chaos. The arrow below the figure shows where the chaos is. (C) Frequency jumps. The arrow points to the jump. (D) Mixed. This category corresponds to the presence of more than one nonlinear phenomenon. This example shows one of the various possible combinations of two nonlinear phenomena in the same vocalization, frequency jump at the first part of the call (shown by the arrow) and deterministic chaos in the second (shown by the arrow below the figure). (E) Example of a break in a complex call (deterministic chaos). The arrow below the figure shows the silent period. Recordings made with the Sennheiser ME 66 microphone.
Contributor Notes
Associate Editor: J. F. Schaefer.