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Aposematic prey is characterized by the fact that individuals are warningly-coloured and unpalatable to predators. However, variability in antipredator defence may occur within one species. The presence of intraspecific variation in antipredator defences is called automimicry. Automimics can be palatable or have a different level of quantity or quality of chemical defence. One of the ways through which the variability arises is for instance consumption of specific plants which defence against predators by means of sequestration. Intraspecific variation in antipredator defence affects the behaviour of predators that can distinguish between palatable of unpalatable prey. Chemical defence is costly for unpalatable individuals. Palatable individuals on the other hand save much energy by simply resembling unpalatable individuals of the same species.

An aposematism is a type of defence mechanism, by which a prey demonstrates towards predator that it is unpalatable and toxic. The reactions of predators towards chemical warning signals of prey differ due to the quantity and a combination of signals showed by prey, the predator species and its primary orientation. Most of works tested reactions of birds towards gustatory and olfactory stimuli, often in combination with signals from other modalities. Although the birds are predators which orientate primarily visually, olfaction, gustation and chemesthesis significantly helped them with determining unpalatable food. Among other tested predators were fish, amphibians, reptiles, mammals and invertebrates and their reactions towards the same chemicals of prey are noted for comparison. The main chemicals used in the experiments regarding birds were denatonium benzoate (Bitrex), quinin and pyrazines. Predators often showed an aversive behaviour, neophobic reactions, accelerated learning and more effective memorizing of the unpalatable prey if it was presented together with chemical signals. Some of the predators were able to control their toxin intake relative to the amount of toxin ingested or to discriminate between palatable and unpalatable food according to the chemical concentration in it. Key...