During the right season, you can see tons of Sierra newts crossing the trail to Hite's Cove. These cute little guys are brightly colored to warn predators that they are coated with tetrodotoxin and have it in many organs. One study estimated that the neurotoxin in a single newt could kill between 1200 and 2500 mice. In other words, don't eat these guys.
They are usually terrestrial except during their breeding phase. They belong to the salamander family, but unlike many salamander, newts breathe with lungs, rather than through gills.
There's a nice writeup on the California Herps site: Sierra newt.