What kinds of signals do animals use to share information?

Animals utilize a variety of signals to share information, which helps them make decisions regarding survival, reproduction, and social interaction. These signals are categorized into several primary modalities:12

• Sound: Animals produce sounds to communicate across distances, around obstacles, or in dark environments. Techniques include stridulation (rubbing body parts together) in arthropods and the use of specialized vocal structures in vertebrates. Because sound frequency and wavelength are constrained by body size, smaller animals typically use higher-frequency sounds, while larger animals can produce lower-frequency signals.34
• Visual: Visual signals rely on ambient light and include color patterns, postures, and movements. Animals may enhance these signals by increasing contrast with the background, such as using black-and-white patterns or specific pigments. In environments with little light, some species use bioluminescence to generate their own light.423
• Chemical: Animals release pheromones—chemicals that elicit specific reactions in others of the same species. These are used for functions like marking trails, signaling danger, or attracting mates.54
• Tactile: This involves physical contact, such as grooming, or the transmission of vibrations through a substrate (like webs or plant stems) or a medium (like water eddies).4
• Electrical: Certain fish species, such as those in the orders Mormyriformes and Gymnotiformes, generate electric fields to navigate and communicate with others.4

These signals are not merely incidental noises but are evolved actions or structures specifically designed to convey information to a receiver.2