Many poisonous and toxic animals are brightly coloured, and other animals and predators are instinctively wary of brightly coloured animals. This is called warning colouration or aposematism. Described more scientifically, these colouration adaptations are to deter predators by using a warning signal, which indicates that consuming the prey item would be unprofitable. Nudibranchs back up this warning by secreting poisons that would be toxic or foul-tasting to predators. Nudibranchs have developed this strategy probably because it has a lower energy cost compared to developing a protective shell.
