Straight-crested penguins throw their firstborn out of the nest. Scientists finally figured out why

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 Straight-crested penguins throw their firstborn out of the nest. Scientists finally understand why

For a long time, scientists could not understand why representatives of this species refuse their first egg.

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The first study of straight-crested penguins (Eudyptes slateri) was carried out back in 1998. Today it is considered the most extensive of all existing – the main problem is the fact that representatives of this species live on remote uninhabited islands. More than 20 years ago, scientists noticed that penguins were literally throwing away their firstborn, focusing on raising a second egg. However, until now this mystery has not been solved, writes Science Alert.

The world's least studied penguins lay two eggs per season each year, only to give up on the first. Such strange behavior was noticed in 1998, when scientists studied more than 113 nests. It turned out that in 80% of first-born eggs are lost before or on the day of laying the second egg. The remaining 20% ​​was lost over the next week.

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It is curious that in most cases the females simply laid the first egg outside the nest and only in rare cases in it. Scientists decided to conduct an experiment and fenced 14 nests with a circle of stones to protect the firstborn. Alas, it didn't help. In 100% of the nests, regardless of whether they were in a circle, the first eggs were lost or even destroyed.

Scientists were interested in such a strange behavior of penguins and they decided to study in more detail the factors that push representatives of this species to infanticide. During the study, scientists found that in most cases the first egg is much smaller than the second. According to scientists, this factor makes mothers prefer the second egg.

Squashy penguins throw their firstborn out of the nest. Scientists finally figured out why

 Straight-crested penguins throw the firstborn out of the nest. Scientists finally figured out why

Until now, there have been two main theories explaining why females get rid of the first egg and prefer the second.

  • The first theory suggests that firstborns are lost in the struggle during the nursing period. However, researchers believe that this is not very close to the truth – judging by the behavior and hormone levels of penguins.
  • The second theory suggeststhat the first-born are a kind of insurance in case of loss of the second egg. However, researchers believe that this explanation is not very close to the truth.

The fact is that the ancestors of straight-crested penguins also laid two eggs per season. Scientists believe that if food becomes less available in the future, then the birds will stop laying a second egg, but for now, natural selection plays on the side of the second eggs, making them larger, and therefore more tenacious.

The researchers found that the numbers of these subantarctic penguins have declined sharply over the past half century. The reason for this is insufficient food – females simply cannot find the necessary amount of krill and squid to feed both chicks.

As a result, they had to make such sacrifices. Physiologically, penguins are not able to lay a second egg without laying the first – so scientists believe that the best way for females to adapt to new conditions is to reduce investment in the firstborn. Apparently, that's exactly what they did.