The crested penguin sacrifices its first egg for the benefit of the second


Dn the hostile climate of the extreme South, reproducing but above all feeding one’s offspring is a feat. The penguins have understood this well. The most massive of these cold-sea birds – emperor and king penguins – lay a single egg each year. The others grow to two. Their cousins, the penguins, recognizable by the egrets on each side of their head, stopped halfway: the females lay two eggs… but only let one hatch. The interest of such a practice? For four of the seven species, which incubate the first egg as soon as it is released, scientists have decided: it is life insurance. Laid a few days later, the second is entitled to the attention of the parents only if misfortune has happened to its predecessor. But three other species do the opposite: they shun the first egg and invest everything in the second.

What does such behavior mean? Any masterpiece requires a draft, respond painters and cadets in search of recognition. In an article published on October 12 in the journal PlosOne, a team from the University of Otago, New Zealand, tried to go further by closely studying the reproduction of the crested penguin. For this, the biologist Lloyd Davis took up “the oldest dataset ever collected on these isolated and poorly understood birds”the one he had collected during a long expedition to the Antipodes Islands in 1998.

On these uninhabited lands, lost some 800 kilometers south-east of New Zealand, lives, or rather survives, Eudyptes slateri, the scientific name for the crested penguin. After three and a half days of navigation and a tumultuous landing, Davis and his colleagues had been able to observe, from September to November, the entire breeding season, from courtship displays to egg hatching. A particularly rich material. Except that, back in Otago, Lloyd Davis had changed his life to set up the university’s wildlife film department. Buried, the data. But “in the face of the constant reduction of the population of this species”the biologist decided to reopen his notebooks and publish.

A second 85% larger egg

First observation: none of the first 200 or so eggs that scientists observed hatched. 40% of them have never been brooded, others are lost, in other words roll out of the rudimentary nest erected by the birds. Still others are destroyed once the second egg has been laid, an average of 3.5 days later. A significantly larger egg than the first: 85% more mass, the largest difference so far recorded in the different species of penguins.

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