Aposematism

The gold tree climber is one of the aposematically colored animals

In behavioral biology, aposematism , sometimes also called warning coloration , describes the conspicuous coloration of animals with which potential predators not only signal presence, but also inedibility and / or defenselessness. Aposematism is therefore the opposite of camouflage .

Aposematically colored animals are either defensive because they have poisonous spines or other active defense mechanisms, or they taste unpleasant, are inedible or even poisonous. Usually a single encounter is sufficient for potential predators to develop a lifelong aversion to aposematically colored animals. In particular with butterfly caterpillars one can find well-camouflaged caterpillars and caterpillars, e.g. B. the caterpillar of the alder bark owl , which signal their inedibility via a conspicuous color. Other examples are the scorpion fish , the puffer fish , moray eels , poison dart frogs and some local amphibians such as salamanders and toads .

Illustration by Henry Walter Bates (1862). The upper and third rows show Dismorphia species ( mimicry ), the second and the last row show Ithomiini species (Aposematism).

Since predators usually have to develop the aversion to aposematically colored species, individuals of such species are repeatedly injured or even eaten. They serve as a teaching model for the predator. However, these conspicuous coloring costs are distributed across all individuals in a population. The evolutionary development of aposematism, however, is still controversial. A warning color that occurs for the first time in an individual due to a mutation increases their risk of predation compared to camouflaged individuals . One possible explanation is that the inedibility or defenselessness develops first and warning colors develop only with higher population densities.

Some species that are edible and not defensible reproduce the characteristics of aposematic species in order to deter potential enemies. This strategy is known as mimicry .

Poisonous octopuses can increase their aposematism if necessary by additionally pulsing the warning patterns in muscle cells, as is the case with the blue-ringed octopus .

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  Scorpion fish

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  Puffer fish

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  Moray eels

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  Poison dart frogs

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  fire salamander

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  Toads

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  Great blue-ringed octopus ( Hapalochlaena lunulata )

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  Larva of the alder bark owl

Individual evidence

1. ↑ Yfke Hager: Blue-ringed octopus flexes muscles to flash fast warning signals. In: The Journal of Experimental Biology , 2012.