Deimatic defence is when prey startle predators and so get time to escape. The predator gets a shock, and often jumps back when startled. Many prey use this tactic when a predator gets close. It is an anti-predator defence.
Displays are classified as deimatic or aposematic by the responses of the animals that see them.
- Where predators are initially startled but learn to eat the displaying prey, the display is classed as deimatic, and the prey is bluffing;
- Where they continue to avoid the prey after tasting it, the display is taken as aposematic, meaning the prey is genuinely distasteful.
In the second case, the behaviour is both deimatic and aposematic. It startles the predator, and the display truly indicates the prey is bad to eat.
Deimatic defence Facts for Kids. Kiddle Encyclopedia.