There are 18 species of penguins in the world. We are here to see just one species: the emperor penguin. There are two species within their genus: king and emperor — they have many common features and look very similar, however, the emperor is the largest.
POPULATION: Kings are subantarctic and live on the islands around Antarctica; their population is estimated at 1.6 million pairs. Emperors are only on Antarctica’s coasts within 54 colonies; their population is estimated at 238,000 pairs. Lifespan is about 20 years.
BREEDING CYCLE: Kings and emperors only lay one egg per breeding cycle. The emperor breeding cycle is 8 months ~Apr-Dec — matches the sea ice cycle.
December - March: They use ~3-4 months to get fit (=fat, they double their body weight) to be able to endure the 8mo breeding cycle. The penguins come to shore to breed ~mid March and they walk or toboggan (slide on their bellies) to get to the colony. They’re all together by late March.
April: Courtship. They practice seasonal monogamy = one partner per breeding season, but not annually; only ~15% of pop stays together year after year. Other penguin species, except kings, have ~80% monogamy. This could be because they don’t have nests or could be because there are more females in the population. Many males don’t make it through the winter/incubation period.
Breeding is difficult - they’re very fat, it’s crowded, and other penguins interrupt.
May: Egg-laying. They produce thick shells (0.8-1.4mm) that they incubate on their feet. Then comes the very important egg transfer. Females lay the egg and then very carefully pass the egg from her feet to her mate’s feet. Up to 25% of eggs are lost during this process. The females leave the colony to feed - she is exhausted and skinny after producing the egg, so she will walk kilometers to the ocean to feed and regain body fat. Because of this, it’s not safe for females to take turns incubating egg.
June-early Aug: Egg incubation by the males. Males have a brood patch where bare, featherless skin transfers heat to the egg. Males will rotate the egg on their feet to keep all parts warm. They will sleep a lot while incubating and undergo a ~10% reduction in metabolic rate. They huddle together to keep warm and the mass of males is always moving in a dense pack to avoid heat loss. In the huddle, the heat can be high (37.5C), so they rotate from the outside to the inside of the huddle and back. The huddles only last about 2 hours to avoid over-heating, plus it’s also good for their metabolism. When in a huddle, a male may lose 150g/day of metabolic mass vs. a lone, non-huddling male would lose 300g/day.
Mid-July-mid-Aug: Hatching. Hatchlings stay on the male’s feet to avoid the ice. The chick is hungry, so males make a “crop milk” from the lining of the male’s esophagus (~60% proteins, 30% fats). Chicks will be fed a few days and will start to appear out from under the male’s feet. Males are waiting for the females to return to help feed the chick. At the end of the 4 month fast, males have lost 45% body weight (~9% body fat is left (was 45% when they arrived) — they still have to walk to a place to feed which can take days — they seek out openings in the ice that remain year after year. Leopard seals know that males will be making their way to these openings and wait to feed on these skinny guys.
Females don’t digest the food they have taken in, so when they arrive back to the chicks, they will feed the chicks what they caught at sea.
There will be different sized chicks because females don’t lay eggs at exactly the same time.
Aug-mid-Nov: Chick-rearing. At about 30 days, chicks will start to explore and parents need to watch them. At about 45-60 days, the parents will not allow the chick onto their feet anymore - they are now adolescents. Parents leave the chicks so that they can go feed and bring back food. The chicks form their own huddles and creshes. Unfortunately, some chicks can’t wait for their parents to return and starve. Also, gulls and skuas will take chicks.
As the ice melts, parents’ commute is shorter to the open water. They give 20% of take to chicks and keep 80% to themselves (they need to prepare for the next breeding season).
Nov-Dec: Chick molt and departure. By early Dec, the chicks will follow the parents to the water and then the parents stop feeding chicks. The chicks will molt their downy feathers for waterproof feathers and fledge. They’re hungry, so they will start to swim. They will begin to wander and not come back to land, only coming back to land to breed. They have ~60% survival rate during the first year - the chicks are so small and can have trouble feeding or they will be fed upon. They will first return to the colony at 4 years and will attempt to breed the next year.