The King penguin (Aptenodytes patagonicus) is a large species of penguin, second only to the emperor penguin in size. The King penguin stands at 70 to 100 cm tall and weighs from 9.3 to 18 kg. Thus the average weight of the king penguin is similar or just slightly higher than that of the largest living flying birds.
King penguins eat small fish and squid and rely less than most Southern Ocean predators on krill and other crustaceans. Fish constitute 80–100% of their diet, except in winter months of July and August, when they make up only 30%. Lanternfish are the main fish taken, and cephalopods, like the hooked squid and the sevenstar flying squid, are an important food source. On foraging trips king penguins repeatedly dive to over 100 metres, and have been recorded at depths greater than 300 metres.
The majority (around 88% in one study) of dives undertaken by king penguins are flat-bottomed; that is, the penguin dives to a certain depth and remains there for a period of time hunting (roughly 50% of total dive time) before returning to the surface. Its average swimming speed is 6.5–10 km/h. King penguins also porpoise, a swimming technique used to breathe while maintaining speed. On land, the king penguin alternates between walking with a wobbling gait and tobogganing—sliding over the ice on its belly, propelled by its feet and wing-like flippers. Like all penguins, it is flightless.
King penguins breed on the subantarctic islands at the northern reaches of Antarctica, South Georgia, and other temperate islands of the region. The total population is estimated to be 2.23 million pairs and is increasing. The largest breeding populations are on the Crozet Islands, with around 455,000 pairs, 228,000 pairs on the Prince Edward Islands, 240,000–280,000 on the Kerguelen Islands and over 100,000 in the South Georgia archipelago. Macquarie Island has around 70,000 pairs.