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Nature's Color for Warnings

Warning coloration, or aposematism, is a defense system in which prey species have evolved striking colors and patterns to warn potential predators that they are toxic. In addition to bright colors, the prey species may also be characterized by strong odors, sounds or behaviors that work together to provide a distinct warning. Other species that are not toxic have co-evolved warning colors and patterns through the mimicry of this adaptation to reduce predation. Red, yellow, orange and black are the most dominant colors used in aposematism.

Aposematism in Red
- The strawberry poison dart frog, Oophaga pumilio, is a striking example of aposematism found in the lowland rain forests of Central America and Puerto Rico. With a brilliant strawberry-red head and body and blue or black lower parts, these amphibians display a clear indication of their relative toxicity. The noxious alkaloids secreted from their skin result in very few natural predators, although these toxins are weaker than those found in other closely-related species.
Aposematism in Yellow
- Aposematism is widespread in insects, and is illustrated by the conspicuous color patterns of the yellow-and-black paper wasp. These bands of color contrast remarkably well, making these wasps visible in a variety of situations. Within the species, color variations can indicate the relative toxicity of the individual to predators. Studies have shown that those wasps with the brightest colors have the largest poison gland associated with the stinger.
Aposematism in Orange
- The bright orange color of monarch butterflies serves as a warning to potential predators. These butterflies and the monarch larvae are both poisonous to vertebrates due to chemicals ingested in the larval diet. Monarch caterpillars feast on a variety of milkweed species that contain compounds known as cardenolides that make the butterflies and caterpillars bitter-tasting and toxic The viceroy butterfly is not harmful, but has evolved similar color patterns to the monarch and benefits from the predator avoidance lesson the monarch's toxicity provides.
Aposematism in Black and White
- Animals may use bright hues or contrasting patterns to provide visual warnings to predators.
  
  Although aposematism is less common in mammals when compared to other animal groups there is no mistaking the sharply contrasting black-and-white warning coloration in skunks. The function of these markings is to warn attackers that it is best to stay back to avoid getting sprayed. This visual warning is accompanied by tail raising, feet stamping, hissing and scratching as well as certain postures that indicate a skunk is ready to spray. The extreme discomfort caused by this spray provides the learning experience predators need to avoid future contact with these creatures.

Animals & Science