The term “sign stimulus”, or “releaser”, is used to denote alcock animal behavior pdf free simple feature of a complex stimulus that can elicit a FAP. For example, the red belly of a male stickleback elicits a head-down, attack behaviour in other male sticklebacks.
This same response can be elicited by artificial models or objects that contain the sign stimulus of red, for example, a red coloured card. The term “sign stimulus” is used to denote a feature of an animal’s environment that elicits a particular response. During spring, male sticklebacks change colour, establish a territory and build a nest. They attack male sticklebacks that enter their territory, but court females and entice them to enter the nest to lay eggs. Tinbergen used crude models of sticklebacks to investigate which features of male and female sticklebacks elicited attack and courtship behaviour from male sticklebacks. Tinbergen’s main findings were that male sticklebacks responded in a relatively invariant way and attacked a model with a red belly, but in contrast, courted a model with a swollen belly. The sight of the displaced egg is the sign stimulus and elicits the egg-retrieval behaviour.
If the egg is removed from the goose during the performance of egg-rolling, the bird often continues with the behavior, pulling its head back as if an imaginary egg is still being maneuvered by the underside of its beak. FAPs have been said to be “hard-wired” in animals’ brains. For instance, the greylag goose’s egg rolling behavior is so essential to the survival of its chicks that the fitness of the parent bird is increased by the behavior being relatively invariant. A stickleback will attack any male fish who enters his territory while the female is sexually receptive, reacting to their red colour, while the female stickleback triggers behavior in the male resulting in the fertilization of her eggs. Relatively invariant behaviors are also predictable, which can lead to their exploitation by humans or other animals. There are exceptions to fixed action pattern rules. For example, male blond ring doves isolated from their own species will resort to courting a pigeon, then a human’s hand, and finally expressing courtship activity alone in their box if they are left alone for a long period of time.