Emperor Penguin

Emperor penguins rely on a counter-current heat exchange system in their feet, a trait penguins use to withstand extreme cold without losing body warmth. Warm arterial blood heading to the feet runs alongside cooler blood returning to the body, and heat passes from the outgoing blood into the returning blood, so less warmth is lost to the ice. This keeps the feet just above freezing while preventing dangerous heat loss. Long, thick tendons run down to the feet while the leg muscles sit inside the body, so the tendons are less easily affected by cold. By minimizing heat lost to the environment, penguins conserve energy during long periods on the ice, where air temperatures can fall to about -40°C (-40°F). This system is one of several adaptations that help emperor penguins thrive in Antarctica’s cold.

Before and during brutal Antarctic storms, emperor penguins form dense huddles of anywhere from about ten to several hundred birds, helping them endure air temperatures near -40°C (-40°F) and howling winds. By pressing tightly together and shuffling positions, they dramatically reduce individual heat loss. Birds on the windward edge work their way around to the sheltered side, so every penguin takes turns inside and outside the group. Research shows the payoff is large: huddling can save penguins roughly 26 to 32 percent more energy than standing alone or in small groups, partly because a huddle shields about three quarters of each bird’s body surface from the elements. Inside a dense huddle, temperatures climb well above the air outside. Through cooperation and constant motion, emperor penguins endure conditions that would be lethal to most other species.

Emperor penguins breed on ice rather than land, almost always on stable pack ice near the coast, sometimes up to 18 km (11 mi) offshore. Only three land colonies have been reported to date, and since 2009, some colonies have also formed on ice shelves. To reach their breeding sites, adults may walk 50 to 120 km (31 to 75 mi) from the edge of the pack ice. These frozen platforms provide stability for raising chicks and safe access to the ocean for feeding. Satellite images show the population lost about 10% (more than 20,000 adults) between 2009 and 2018, with record-low sea ice since 2016. Because they depend so heavily on sea ice, early break-up and ice loss are the main driver of their decline, and the IUCN now lists the species as Endangered.

Emperor penguin breeding colonies can hold up to several thousand birds, gathering on stable sea ice through the Antarctic winter. These colonies become essential for survival, as birds huddle together to conserve warmth and shield themselves from relentless winds. Males rotate through the middle, sharing the warmest spot. Because emperors have no fixed nest sites, adults rely on calls to find mates and chicks among the dense crowd. Emperor penguins show the widest variation in individual calls of any penguin species, and their calls use two frequency bands at once. Despite the harsh conditions, the colony remains active, with parents taking turns caring for eggs and chicks. Researchers know of 66 breeding colonies around Antarctica as of 2022. This collective resilience allows emperor penguins to raise young in one of the world’s most unforgiving environments.

By the time the egg hatches, the male has gone roughly 120 days without eating since arriving at the colony, losing about 12 kg (26 lb) while keeping the egg warm. The female returns from weeks spent feeding at sea, finds her mate by his call, and takes over caring for the newly hatched chick by regurgitating stored food. Until she arrives, the father can feed the chick a milky secretion for only a few days. If she is delayed, the chick can die. An estimated 10 to 20 percent of females do not return from sea. Once relieved, the exhausted male heads to the ocean for three to four weeks, returning later to continue supporting the growing chick. This precisely timed exchange is one of the most remarkable examples of parental care in birds.

About 45 to 50 days after hatching, emperor penguin chicks are old enough to be left alone and gather into groups called crèches. These clusters provide warmth and protection while both parents are away hunting at sea, returning periodically to feed them. By huddling together, chicks reduce heat loss, an advantage during the Antarctic winter. Crèches can range from about a dozen chicks to several thousand, and they allow parents to forage efficiently without risking their chick’s survival. Chicks beg for food with a distinctive whistle, and parents recognize their own chick’s call among the crowd. Chicks begin molting into juvenile plumage in early November, a process that can take up to two months and often isn’t finished before they leave the colony. The crèche is a vital stage on a chick’s journey toward independence.