When attacked, the common toad puffs up its body and stands with its back end raised and its head lowered. Its main means of defence is a foul tasting secretion. It has a bufotoxin called bufagin and is enough to keep away many predators. Grass snakes seem to be unaffected by it. Other predators of adult toads include hedgehogs, rats and mink, and even domestic cats. Birds that feed on toads include herons, crows and birds of prey. The tadpoles also have noxious substances which keep fishes from eating them but not the great crested newt. Aquatic invertebrates that feed on toad tadpoles include dragonfly larvae, diving beetles and water boatmen. These usually avoid the noxious secretion by puncturing the tadpole's skin and sucking out its juices.