In icy regions, researchers find polar opposite in predators

[Cara J]

Take a cruise from the equator to the poles and you might notice some important changes in marine ecosystem. Species diversity is greater in the tropics, and it dwindles as the climate becomes colder. But biologist John Grady realized something else was happening, too. Marine mammals and birds actually become more common relative to large fish and sharks closer to the poles. Compared to cold-blooded predators, “warm-blooded animals don’t have a temperate peak,” Grady said. “They have a polar peak. They get relatively more diverse as you get closer and closer to the poles.” In the topics, top marine predators tend to be cold-blooded species, like sharks. Move to the poles and they tend to be warm-blooded animals, like whales, dolphins, seals and birds. A postdoctoral researcher at Michigan State University, Grady wondered why. What he found, he believes, could have important conservation impacts for polar predators. “In some sense, it’s a very simple idea,” said Grady, lead author of a paper on this phenomenon published in Science. Put simply: it pays to be warm-blooded in a cold climate. “It gets easier and easier to eat and not get eaten as you move toward the poles,” Grady said. Cold-blooded prey species [...]

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