 Amphibians have soft bodies with thin skins , and lack claws , defensive armour , or spines . Nevertheless , they have evolved various defence mechanisms to keep themselves alive . The first line of defence in salamanders and frogs is the mucous secretion that they produce . This keeps their skin moist and makes them slippery and difficult to grip . The secretion is often sticky and distasteful or toxic . Snakes have been observed yawning and gaping when trying to swallow African clawed frogs ( Xenopus laevis ) , which gives the frogs an opportunity to escape . Caecilians have been little studied in this respect , but the Cayenne caecilian ( <unk> <unk> ) produces toxic mucus that has killed predatory fish in a feeding experiment in Brazil . In some salamanders , the skin is poisonous . The rough @-@ skinned newt ( Taricha granulosa ) from North America and other members of its genus contain the neurotoxin tetrodotoxin ( <unk> ) , the most toxic non @-@ protein substance known and almost identical to that produced by pufferfish . Handling the newts does not cause harm , but ingestion of even the most minute amounts of the skin is deadly . In feeding trials , fish , frogs , reptiles , birds and mammals were all found to be susceptible . The only predators with some tolerance to the poison are certain populations of common garter snake ( Thamnophis sirtalis ) . In locations where both snake and salamander co @-@ exist , the snakes have developed immunity through genetic changes and they feed on the amphibians with impunity . Coevolution occurs with the newt increasing its toxic capabilities at the same rate as the snake further develops its immunity . Some frogs and toads are toxic , the main poison glands being at the side of the neck and under the warts on the back . These regions are presented to the attacking animal and their secretions may be foul @-@ tasting or cause various physical or neurological symptoms . Altogether , over 200 toxins have been isolated from the limited number of amphibian species that have been investigated . 
