Adjustments to facilitate communication in noisy environments

Animals communicate with sounds, odors, and smells to attract mates, defend territories, or warn against predators. Communication signals thus provide vital functions for reproduction and survival, yet they are often used in environments with high or fluctuating noise levels. Natural conditions, such as waterfalls, heavy rains, or winds, can create high levels of acoustic, visual, and vibratory noise and have shaped animal communication systems during their evolutionary history. Nowadays, human activities also create stimuli such as the sound made by transportation vehicles, or light emitted at night by streetlamps that force animals to adapt their signaling behavior. In this chapter, we review the various ways in which animals are affected by noise in their living environment and outline how they can cope with it. We distinguish between the effects of noise on the receiver and the producer of communication signals in different perceptual systems, such as the acoustical, visual, and chemical domain. We review some evidence that noise, as well as the signals and cues it can affect, is not restricted to a single modality but that animals often combine information across senses. We close off by providing some interesting avenues for studies on multimodal communication and multisensory pollution in animal research.