Salamanders have toxic skin secretions as a line of defense against predators. I would say their first line of defense is how brightly colored salamanders often are. The bright colors of salamanders (and many other brightly-colored toxic organisms such as certain species of frogs) serve as a warning to predators. Salamander skin is also slimy, making it difficult to hold onto them. Furthermore, the slimy coating may taste bad or be quite toxic, so predators quickly learn not to pursue that species of salamander.

Salamander's skin is poisonous for protection, so that other animals (like garter snakes) won't eat them.