An Antarctic penguin, closely related to the gentoo and chinstrap penguins, is the Adélie penguin (Pygoscelis adeliae). It, along with the emperor penguin, is the most common penguin species as well as the most southerly distributed of all penguins. Adélie penguins are found mainly in many breeding colonies along Antarctica’s rocky, ice-free coasts during the warmer months; colonies also exist on the islands of South Shetland, South Orkney, and South Sandwich. They move northward to forage in areas of open water in the pack ice throughout the winter months. A relatively small species with a black back and head, a white front, and a distinctive white ring around the eyes is the Adélie penguin. It is named after Adélie Land, named after Adèle Dumont d’Urville, who married Jules Dumont d’Urville, the French explorer who first discovered this penguin in 1840. Adélie penguins, with a diet of primarily krill and fish, gain their food through both predation and foraging. The Adélie penguin’s one curious trait is its unwillingness to be the first person to reach the water. At the water’s edge, this species is known to establish dense groups waiting for a person to either fall or be forced into the water. Only after the first person is seen swimming safely away to feed do the others follow in the party. This action is believed to be used by leopard seals, killer whales, and other large animals to prevent predation. There are no natural land predators for Adélie penguins and they are highly curious about individuals. They also walk straight up to scientists as if they were doing their own studies. The genus split from other penguin species about 38 million years ago, around 2 million years after the ancestors of the genus Aptenodytes, is suggested by mitochondrial and nuclear DNA data. In turn, about 19 million years ago, the Adélie penguins broke off from the other members of the genus.
Adult Adélie penguins are 70-73 cm (approximately 28-29 inches) long and weigh 4-6 kg (approximately 9-13 pounds), with males slightly taller and heavier than females. The bird’s head, throat, back, and tail are covered by a continuous region of black feathers, while its entire ventral (front) side is composed of white feathers. Other distinguishing features include elongated feathers on the back of the head that can be raised to form a crest and a bill colored black and dull orange, apart from its prominent white eye-ring. In comparison, juveniles have a white throat and black eye bands. Adélie penguin chicks’ feathers vary from light gray to dark black. While Adélie penguins live mostly on the Antarctic continent (and a few related islands), rather than on the ice, they mate and nest on rocky shores. The two parents take turns taking charge of a clutch of two eggs laid in a stone nest. When the eggs are incubated by one parent, the other parent feeds them. In females, the average age of sexual maturity is three years, while at age four, males become sexually mature. The two sexes also return to breed in the colony of their birth. The penguins of Adélie can live as long as 16 years. Adelie penguins are foraging predators that take several different items of prey, but krill is their favorite source of food. However, their dependency on this particular source of food is a relatively recent phenomenon that seems to correlate as a result of overhunting with the decline of other krill predators (e.g., fur seals and baleen whales). Regardless, the current diet of the Adélie penguin consistently contains many species of krill. They are known to undergo long, winter migrations in search of food while individuals are not nesting, remaining close to the growing ice edge and using the ice to rest. Small marine species, such as shrimp-like krill, feed on Adélies, but also consume fish and squid. In pursuit of such a quarry, they are known to dive as deep as 575 feet, while they normally hunt less than half that deep in much shallower waters. Adélies are sleek and powerful swimmers, like other penguins. To order a meal, they will drive 185 miles round-trip. There are more than 2.5 million breeding pairs of Adélie penguins in the world, by some estimates. Studies show that several populations are rising. Much of this increase has been due to the break-up of ice shelves along with certain parts of the Antarctic coast, especially since the 1990s on the Antarctic Peninsula. The penguin Adélie is the subject of several scientific studies and is commonly considered to be one of the best penguins studied. For several decades, researchers have been researching Adélie penguin behavior. Unfortunately, the ongoing expansion of research facilities decreases the breeding habitat, possibly leading to the status of this species as nearly endangered. Additional ice-free habitat for Adélie penguins has been created by the loss of ice coverage.