As every year, in the month of December, the Bay of Mariners, on the French island of Possession, is full: thousands of royal penguins flock to this isolated territory in the Indian Ocean to reproduce, although climate change threatens them. This species, recognizable by its black and white plumage topped with a yellow plume, hardly survived the massacre suffered between the end of the 19th century and the first half of the 20th century at the hands of sealers in the Crozet archipelago.
“Towards the end”, when there were no more seals to hunt, “the hunters used them as fuel, burning them to melt the seal blubber in cauldrons. For a short period, they made penguin oil. But it was not of good quality”, explains Robin Cristofari, a researcher specializing in these birds at the University of Turku (Finland). “The species was close to extinction”, recalls the scientist, observing the colony on this island located in the French Southern and Antarctic Territories (TAAF). The population was reconstituted in the 20th century, “but it has stagnated for 20 years”, explains Cristofari, adding: “after a first wall, the species ran into another more insidious one: global warming”.
Reproductive journey
The royal penguin spends its life at sea and only returns to land to lay its eggs. For this, it needs a dry place but at a reasonable distance from the polar front, the area where the hot and cold waters of the Indian Ocean meet, which is where it will feed on plankton and fish.
The polar front is located 350 kilometers south of the Crozet archipelago in winter, but in bad, very hot years it can go up to 750 kilometers away, too far to go to feed and return in time to take over the pair and feed the chick. “The success of reproduction depends on the distance from the polar front”, summarizes Robin Cristofari.
With climate warming, the front is shifting south and eventually Crozet could become uninhabitable for these penguins, which will need to move to other islands further south. Of the nearly one million pairs registered in the world, half breed on the Crozet Islands and 300,000 on the Kerguelen Islands, 1,400 km further east. Although the researchers do not believe that the species is in danger of disappearing “in the next 50 years”, its way of life could be seriously altered, says Cristofari.
Alternate custody
A penguin, which on average lives 25 years, has its first chick at 6 or 7 years old. “Playful and curious”, it will huddle together in gigantic colonies with the egg balanced on its feet and its belly on top. Males and females share the work 50/50 and pass the egg to hatch, a dangerous time as predators lurk.
In a classic cycle, males and females arrive at Crozet in early November, meet and mate. The female will lay an egg, hand it over to the male, and go to the sea to feed. During the 50 days that incubation lasts and in the first month of the chick’s life, they care for it alternately: they can go up to a month without eating to care for their egg. The chicks are well fed until May and then fast during the southern winter, although the parents will feed them from time to time. The young penguins leave the land, spurred on by hunger, 12 months after hatching from the egg.
This alternation of feeding and fasting is of particular interest to researchers. “It is a species that goes from acutely obese to very thin several times a year”, observes Robin Cristofari, something that “for a human organism would be devastating”.
