![]() It’s simpler to just evict, neglect, or destroy the stunted egg than it is to alter their reproductive cycles and restructure the biology of their ovaries. Perhaps they haven’t because it’s the path of least resistance. “One would think that after several million years of evolution, the would have eliminated the first ovulation leading to the A-egg,” says Crossin. The longer each species stays out, the feebler its A-egg, the team reports in a Royal Society journal. Again, this supports the idea that the crested penguins are stuck with laying a tiny first egg because they spend so long at sea. But among the other ten penguin species, there’s no connection between these traits. They found that among the six crested penguins, the species that reproduce quickest after arriving back on land also laid eggs with the most extreme size differences. To test this idea, Crossin and Williams gathered data for all 16 species of penguins that lay two-egg clutches. It’s only the crested penguins that have that unfortunate overlap. By contrast, other penguins begin making eggs weeks or months after they return to land. Once they’re on land, crested penguins can fully devote their energies to egg-making, which is why the B-egg is bigger. Get too close to penguins-chinstrap penguins in particular-and your endearing perception of these birds may be tested, given their penchant for projectile pooping and beating each other up. Hence, their first egg-started while swimming-is small. If females are forced to be speedy swimmers, they can’t properly invest in eggs. Both are intense activities that burn a lot of energy. They reasoned that it’s hard for females to both make eggs and swim fast. ![]() In 2010, Crossin and Williams showed that the female macaronis who reproduce most quickly once arriving-and thus spent the longest time making yolk while at sea-also had the greatest size difference between their A-eggs and B-eggs. This process takes 16 days, and female macaroni penguins will lay their eggs just seven to 14 days after finally making landfall again. ![]() Specifically, they start making the yolk for their eggs while at sea. And it’s during these epic voyages that the females start ovulating, and making their A-eggs. Instead, they swim quickly and continuously over two million square kilometers of frigid waters, searching for food on what has to be one of the longest foraging trips made by any animal. For six long months, they never come onto land. He noted that while most penguins spend the Antarctic winter close to ice, crested penguins head out into the wide open ocean. In 1990, Tony Williams from Simon Fraser University suggested a different idea. “None of these explanations have stood up to experimentation, however,” says Crossin. Others believed that the A-egg might be an “OCCUPIED” sign that tells other penguins that a nest is full. Some thought that the A-egg is insurance, in case the B-egg is accidentally snatched by predators or accidentally damaged by squabbling males. ![]() “For many years, biologists have argued that there must be some adaptive basis,” says Glenn Crossin from Dalhousie University. Why is the A-egg so much smaller than the B-egg? And since it almost always dies, why would crested penguins bother producing it at all? Why not simply concentrate their efforts on a single egg, as the famous emperor and king penguins do? On the off-chance that both eggs hatch, only one of the two chicks ever survives to become a fledgling, and it’s invariably the larger B-chick.Įvolutionary biologists have been puzzling over this bizarre trend since the 1960s. The mother penguin might kick it out of her nest. Because it’s smaller, the A-egg is almost always doomed. It’s smaller by between 18 and 57 percent, a greater difference than in any other bird. The first-let’s call it the A-egg-is always smaller than the second, or B-egg. They produce two in any given breeding season. Instead, you need to watch what happens when they lay their eggs. With their elaborate yellow eyebrows, crested penguins are both unmistakable and slightly clownish.īut to see the strangest part of these birds, such as the macaroni and rockhopper penguins, you shouldn’t look to their comical plumes. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |