Why do Adelie penguins only incubate their biggest egg?

Adelie penguins, commonly found in Antarctica, incubate their eggs for a month, guarding them and keeping them warm. However, the parents instinctively focus on the biggest egg and abandon the smaller ones.

"Female Adelie penguins usually mate only once and lay two eggs every year. They have a lot of enemies in nature, so they don't have enough energy and time to hatch both. They will choose the bigger one to hatch, basically following the law of survival of the fittest. In this way, the chance of success will be relatively higher," said Wu Zhenhua, a nursery staff member at Shanghai Haichang Ocean Park.

The Ocean Park is preparing to welcome its newest batch of Adelie penguin chicks after 15 eggs were laid late last month, a record for the park since it opened.

Nursery staff at the park cherish every egg, though. Those abandoned by the penguin parents are immediately removed and placed in an incubator so that they can all successfully hatch. Staff members constantly adjust the humidity and temperature levels of the incubator, and also simulate the natural hatching process by turning, bumping and drying the eggs.

"Our artificial hatching can greatly increase the success rate of egg hatching, ensuring all eggs are attended to and all chicks can come out," said Wu.

On November 14, the first penguin chick broke through its shell. In the following days, more chicks will break out and meet with visitors. The park has also opened a livestream channel for people to witness the chicks' birth.

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