Instead, they've evolved into flippers. Penguins use highly developed muscles to flap their wings to move forward, and they guide themselves with their tail. That is to say, they launch themselves out of the water, momentarily flying in fluid arches as they continue to swim forward at high speeds like dolphins. Penguins do this in order to breathe, but porpoising also creates air bubbles that reduce friction during swimming. Gentoo penguins are thought to be the fastest of all swimming birds, achieving speeds of thirteen to seventeen miles per hour.
Penguins breed in colonies and can be fiercely territorial.
They breed closely together mostly because there is very little ice-free space. But they are also highly social animals that recognize individuals and return as adults to the rookery where they were born. The colony helps these birds guard, protect, and defend their young. Within these colonies, penguins build rookeries with pebbles and guano. Penguins fall prey to leopard seals, sea lions, and killer whales.