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Cold water rulers

The balance of power amongst marine animals could shift due to ocean warming

Freiburg, Jan 25, 2019

Cold water rulers

Warm-blooded predators such as seals are important for regulating the ecosystem. Photo: kichigin19 -

In ecology, the rule is that biodiversity rises towards the equator and is highest in the tropics. An exception, however, are warm-blooded animals such as seals, whales and penguins in the oceans: Their diversity is increasing towards the North and South Poles. And this despite the fact that they have to warm up their bodies more and the food they need requires a high metabolism. A team led by Dr. John Grady from Michigan State University in the U.S. and the Freiburg biologist Dr. Kristin Kaschner has investigated the far-reaching consequences of the adaptation of warm-blooded predators to cold waters with regard to the distribution of their biodiversity. The researchers published their study in the scientific journal Science.

Using data and theoretical models, the scientists show what an evolutionary advantage warm-blooded predators with their high metabolism have compared to animals in polar regions that are warm and changeable. Since fish, as cold-blooded animals, swim more slowly in cold water, it is easier for seals, whales and penguins near the poles to catch prey and escape predators such as sharks.

The diversity of warm-blooded predators is important for regulating the ecosystem, explains Grady: “However, ocean warming will shift the balance of power in favor of sharks and fish. The populations of mammals and birds will decrease.”


Original publication:
Grady, J.M., Maitner, B.S., Winter, A.S, Kaschner, K., et al. (2019): Metabolic asymmetry and the global diversity of marine predators. In: Science. DOI: 10.1126/science.aat4220 



Dr. Kristin Kaschner
Department of Biometry and Environmental System Analysis
Unviersity of Freiburg
Tel.: 0172/69 78 709