2017-07-02 12:44:13
Why are whales so big? Oddly enough, this question has not received an answer until a few weeks ago. Researchers from the University of Chicago, Stanford University and the US Museum of Natural Science have been able to reveal how and why whales have grown to such enormous sizes.
The feeding method of the whales is extraordinary, since these animals lack teeth. These have been replaced by the so-called “beards”, formed not by bone material, but by thousands of keratin filaments, the protein of nails and horns. The baleen allows the whales to introduce large amounts of marine water rich in living organisms into their huge mouth, water that they then expel with their mouths closed, filtering it through the baleen and thus retaining the organisms inside. The baleen thus allowed more efficient feeding which, added to other factors, led the whales to increase in size.
Interestingly, the increase in size, accompanied by a larger mouth, allowed the largest whales to capture greater amounts of food and grow even larger to their current sizes.
Scientists do not yet know precisely the processes that lead to gigantism in some classes of animals. Several hypotheses have been advanced that try to explain it, one of these hypotheses predicts that, given an adequate availability of food, gigantism should occur soon. To see if this hypothesis is correct, the researchers analyze the fossil record of whales from 30 million years ago. In this way, the researchers analyze hundreds of fossils, belonging to 63 different species of whales.
The results of this study indicate that the gigantism of whales (defined as when they reach lengths of more than 10 meters), arose only about 4.5 million years ago. From then on, not only did the larger whale species appear, but the smaller species disappeared. Clearly, an evolutionary force forced the whales to get bigger and bigger.
Scientists indicate that this rapid growth is due to drastic changes in the availability of suspended food in the oceans, due to major climate changes. Among these changes are the glaciations, which had the effect of concentrating phytoplankton and the small animals that feed on it in the warm regions of the planet. This made it easier for the whales to eat and boosted their growth.
More information on Jorge Laborda’s Blog: When did the whales grow?
Referencia: Graham J. Slater et al. Independent evolution of baleen whale gigantism linked to Plio-Pleistocene ocean dynamics. Proc. R. Soc. B 284: 20170546.
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