Acoustic communication in noise: regulation of call characteristics in a New World monkey

TLDR

Acoustic communication is impaired by environmental noise, prompting animals to evolve adaptations such as increased signal amplitude or duration to maintain signal‑to‑noise ratios and detection probability. The study investigates noise‑dependent vocal plasticity in common marmosets, specifically examining amplitude and duration adjustments. We examined whether marmosets prolong vocal signals in response to increasing background noise. Marmosets raised call amplitude and syllable duration as noise increased, preserving signal‑to‑noise ratio and active space, yet they did not add syllables per call series, marking the first evidence of such vocal plasticity.

Abstract

SUMMARY This study on common marmosets Callithrix jacchus is the first to examine noise-dependent mechanisms of vocal plasticity in a New World monkey. Since acoustic communication can be considerably impaired by environmental noise, some animals have evolved adaptations to counteract its masking effects. The studied marmosets increased the sound level of their spontaneous calls in response to increased levels of white noise broadcast to them. Possibly, such noise-dependent adjustment of vocal amplitude serves to maintain a specific signal-to-noise ratio that is favourable for signal production. Concurrently, the adjustment of vocal amplitude can maintain a given active space for communication. In contrast to some bird species, no noise-induced increase in the number of syllables per call series could be found, showing that an increased serial redundancy of vocal signals was not used to communicate under noisy conditions. Finally, we examined a possible noise-dependent prolongation of vocal signals. This approach was guided by the findings of perceptional studies, which suggest an increased detection probability of prolonged signals in noise by temporal summation. Marmosets indeed increased the duration of their call syllables along with increasing background noise levels. This is the first evidence of such mechanism of vocal plasticity in an animal communication system.