page_title: Amphibian
section_title: Defence mechanisms
hierarchical_section_title: Amphibian / Defence mechanisms
caption_attribution_description: Phyllobates terribilis Deutsch: Schrecklicher Blattsteiger
context_page_description: Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.
  The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in recent decades there has been a dramatic decline in amphibian populations for many species around the globe.
  The earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land.
context_section_description: 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 (Typhlonectes compressicauda) 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 (TTX), 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.
  Poisonous species often use bright colouring to warn potential predators of their toxicity. These warning colours tend to be red or yellow combined with black, with the fire salamander (Salamandra salamandra) being an example. Once a predator has sampled one of these, it is likely to remember the colouration next time it encounters a similar animal. In some species, such as the fire-bellied toad (Bombina spp.), the warning colouration is on the belly and these animals adopt a defensive pose when attacked, exhibiting their bright colours to the predator. The frog Allobates zaparo is not poisonous, but mimics the appearance of other toxic species in its locality, a strategy that may deceive predators.
  Many amphibians are nocturnal and hide during the day, thereby avoiding diurnal predators that hunt by sight. Other amphibians use camouflage to avoid being detected. They have various colourings such as mottled browns, greys and olives to blend into the background. Some salamanders adopt defensive poses when faced by a potential predator such as the North American northern short-tailed shrew (Blarina brevicauda). Their bodies writhe and they raise and lash their tails which makes it difficult for the predator to avoid contact with their poison-producing granular glands. A few salamanders will autotomise their tails when attacked, sacrificing this part of their anatomy to enable them to escape. The tail may have a constriction at its base to allow it to be easily detached. The tail is regenerated later, but the energy cost to the animal of replacing it is significant.
  Some frogs and toads inflate themselves to make themselves look large and fierce, and some spadefoot toads (Pelobates spp) scream and leap towards the attacker. Giant salamanders of the genus Andrias, as well as Ceratophrine and Pyxicephalus frogs possess sharp teeth and are capable of drawing blood with a defensive bite. The blackbelly salamander (Desmognathus quadramaculatus) can bite an attacking common garter snake (Thamnophis sirtalis) two or three times its size on the 
caption: Perhaps the most poisonous animal in the world, the golden poison frog (Phyllobates terribilis) is endemic to Colombia.[141]
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