The skin of many frogs contains mild toxic substances

At first sight, frogs seem rather defenceless because of their small size, slow movement, thin skin, and lack of defensive structures, such as spines, claws or teeth. Many use camouflage to avoid detection, the skin often being spotted or streaked in neutral colours that allow a stationary frog to merge into its surroundings. Some can make prodigious leaps, often into water, that help them to evade potential attackers, while many have other defensive adaptations and strategies.[103]

The skin of many frogs contains mild toxic substances called bufotoxins to make them unpalatable to potential predators. Most toads and some frogs have large poison glands, the parotoid glands, located on the sides of their heads behind the eyes and other glands elsewhere on their bodies. These glands secrete mucus and a range of toxins that make frogs slippery to hold and distasteful or poisonous. If the noxious effect is immediate, the predator may cease its action and the frog may escape. If the effect develops more slowly, the predator may learn to avoid that species in future.[140] Poisonous frogs tend to advertise their toxicity with bright colours, an adaptive strategy known as aposematism. The poison dart frogs in the family Dendrobatidae do this. They are typically red, orange, or yellow, often with contrasting black markings on their bodies. Allobates zaparo is not poisonous, but mimics the appearance of two different toxic species with which it shares a common range in an effort to deceive predators.[141] Other species, such as the European fire-bellied toad (Bombina bombina), have their warning colour underneath. They "flash" this when attacked, adopting a pose that exposes the vivid colouring on their bellies