Poison dart frog
The charismatic colors might catch your eye, but such pizzazz is also nature's way of telling you to stay away. The poison dart frog is among the most poisonous creatures on Earth. The two-inch-long golden poison dart frog, for example, has enough venom to kill 10 adult men, reports National Geographic. Indigenous American Indians used the toxic secretions to poison the tips of blowgun darts. That's how the frog earned its common name.
Scientists aren't sure where the frogs' toxicity comes from. They may gather plant poisons carried by ants, termites, beetles and other prey they eat. Poison dart frogs that are raised in captivity and isolated from native insects don't develop venom.