Aposematism

Aposematism is an anti-predator strategy in which prey advertise their defenses through conspicuous coloration, patterns, or other signals to discourage attacks. The warning signals are typically linked to chemical, physical, or behavioral defenses that make predation costly or dangerous.

Visual aposematism is the most familiar form, with bright, high-contrast colors such as red, yellow, and black. The signals are often honest indicators of toxicity or unpalatability, though not always. In many species the warning coloration is paired with chemical defenses, such as alkaloids or other toxins, to reinforce the message. Examples include poison dart frogs, monarch butterflies, certain beetles, and some snakes.

Predators learn to associate the warning pattern with danger after negative encounters, leading to reduced attacks on defended prey. The effectiveness of aposematism depends on signal visibility, the speed of predator learning, and the frequency of defended prey in the environment, with selection favoring accurate and recognizable signals.

Aposematism is closely related to mimicry. In Batesian mimicry, a harmless species imitates a defended one, while in Müllerian mimicry, several defended species share a common warning pattern. Aposematic signals are distinct from camouflage, which aims to hide prey rather than warn predators.