For many species, chemical communications play a significant role in foraging for food, mating, and competitive interactions. While birds employ plumage, many mammals use scent to similar ends. The difference owes to distance. Whereas birds most easily signal afar by line-of-sight, mammals group in close proximity.
Most animals possess multiple modalities for communicating. The chosen form varies by immediate context. Mammals employ sight and hearing for messages to distant places, scent closer in, and tactile communication as the most intimate.
◊ ◊ ◊
As a social vehicle, chemistry is not just a communications medium. Chemical defense is common among all forms of life.