King Cobras are the only snakes that build a nest for their young, but do so on the ground. The males can grow to be longer than 20 feet. Their only natural predators are the mongoose, and humans. Cobras can inject so much venom in a single bite that they can kill an elephant. (They are aggressive, and will rear up and stand their ground when confronted.) Cobras can hear, although they sense sound through contact with the ground much better than humans.