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Lizards, except geckos, are generally considered voiceless organisms, although some species emit oral sounds. For most of these “vocal lizards”, however, there is almost no information on the characteristics of the sounds, precluding exploration of the functionality and evolution of the sounds. Pristidactylus are known as “grunter lizards” since individuals emit oral sounds under predation risk. We explored the characteristics of the sounds emitted by P. valeriae, recording 17 adults and 1 juvenile when they were threatened and captured by a predator. Only adults emitted sounds with open mouths and displayed aggressive postures, e.g., biting attempts. These sounds correspond to hisses, which lack amplitude or frequency modulation. The lizards emitted longer hisses when threatened than when captured by the predator, which may provide honest information on individuals’ ability to escape. In addition, males may experience higher distress during threats since their hisses had higher aggregate entropy than those of the females. Finally, hissing has been documented in four of the five Leiosauridae genera, the family to which Pristidactylus belongs, suggesting that sound emission is ancestral to the family.

Reproductive isolating barriers are a crucial element in the speciation process. From these barriers, and among those acting early in the speciation process (premating), the ethological ones can play a pivotal role in isolating populations or closely related species. In fact, the high diversity of some taxa has been correlated with an elevated divergence in sexual signals, which facilitates isolation. The present study explored whether variation in chemical signals may contribute to the high diversity of Liolaemus lizards, a genus with more than 290 species. Specifically, population scent discrimination was investigated in two sympatric species, L. tenuis and L. lemniscatus, studying the response of closely located populations most likely from the same genetic lineages. Lizards of both species discriminated between scents of their own and different populations, and in some cases, scents from their own population were preferred. These results suggest a fast evolution of scents and/or of their discrimination, implying that the ethological barriers involving the chemical modality may evolve fast. The studied species, however, differed in the strength of the exhibited population scent discrimination, suggesting that the ethological barriers may evolve at different rates across species. It can be concluded that ethological barriers involving chemical modality may disrupt species’ cohesion, potentially contributing to Liolaemus diversification, in synergy or not with geographical barriers.