Chemical aposematism: reactions of predators towards chemical warning signals of prey

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...