The King penguin is the second largest species of penguin. Females are usually shorter and more lightweight than males. The head of adult individuals is dark, almost black, on both sides covered with orange to orange-yellow colored markings, which have form of spoon. Adult penguins also possess an orange colored patch, which is most intense at the throat of the animal, turning to pale yellow on the upper breast and gradually becoming white on the back of the animal. The back and the flippers are covered with black and gray feathers, having a slight silvery shade. The lower bill has a pinkish-red to orange-yellow colored band, displaying ultraviolet reflectance. The hatchlings are dark brown in color before their first molt. Young penguins generally look similar to adult individuals, though they are colored paler, gaining full adult coloration at about 3 years old.
Generally, these animals inhabit rocky islands in certain parts of the Antarctic Ocean. The penguins breed in areas with relatively temperate climate such as sub-Antarctic islands, northern parts of Antarctica and Falkland Islands.
They are diurnal and social animals, gathering in colonies. Usually, the penguin colonies cover large territories, located in open areas with poor vegetation, since the birds do not tend to climb. In order to forage, these animals travel long distances (up to 500 km) from their breeding areas. Before feeding, King penguins bathe in the ocean. During the daytime, penguins can dive to depths of 100–300 meters, remaining there for about 5 minutes before coming to the surface while at the nighttime, they usually do not dive deeper than 30 meters. While on land, the penguins move either by walking with the characteristic ungainly, wobbling gait or simply sliding over the ice surface on their bellies, pushing themselves with their feet and flippers.
Mating behavior of King penguins can be characterized as serial monogamy. During the breeding season, which takes place in November-December, each penguin mates with only one mate. The female lays a single egg. Then, for about 55 days, both the male and the female take part in the incubation of the egg. When the chick hatches out, both parents care for it for about 30-40 days, until the hatchling joins a group of other chicks or crèche, where it finds warmth and protection from predators. Young penguins are independent at 14-16 months old, reaching sexual maturity at the age of 3-5 years.
One of the threats to this species is human activity within the area of their range, which can cause the introduction of a disease, pest or predator, which, in turn, can lead to the decline of their population. However, the primary threat to the penguins is global warming: the rise of temperatures has already caused a sharp decline in the breeding success of King penguins. In addition, global warming affects also the species that the penguins consume, slowing down the development of marine organisms.
Presently, the overall population of the species is increasing, reaching about 2,230,000 breeding pairs. On the IUCN Red List, the King penguin is classified as Least Concern (LC).