Penguins, like all other birds, do not have teeth. The chicks do have an egg tooth, but this is not a real tooth, but rather a sharp bump on the top surface of the bill which is used to break the egg when hatching. Penguins do have rearward-pointing, tooth-like barbs on the tongue and roof of the mouth.
Penguins communicate by vocalizing and performing physical behaviors called displays. They use many vocal and visual displays to communicate nesting territories, mating information, nest relief rituals, partner and chick recognition, and defense against intruders.
Although emperor penguins are effective hunters, they are also prey to a few Antarctic animals as well. Only a third of the juvenile penguins will make it to their first birthday, falling prey to seabirds like giant petrels or skuas. In the water, both juveniles and adults are eaten by leopard seals and killer whales.