Arabia Weather - Whales are large, and enormously huge. The size of fin whales can reach 140,000 pounds. While bowhead whales reach the size of 200,000 pounds. As for the blue whale, it can weigh a whopping 380,000 pounds - making it the largest creature that has ever lived.
For all the time whales have amazed us with their huge size, everyone has been wondering how did whales get so big?
In one study, a team of researchers investigated the massiveness and gigantism of barley whales, which include blue whales, bowhead whales, and fin whales. They found that marine mammals became large relatively recently. During the past 4.5 million years. The reason is climate change, which has allowed whales to overeat.
Whales have an interesting evolutionary history. They started out as mammals that lived on land and had hooves about 50 million years ago. Over many millions of years, they evolved into marine creatures with the development of fins. Between about 20 million and 30 million years ago, some of these ancient whales developed the ability to filter while feeding, meaning they could swallow swarms of small prey in one huge gulp. With this ability to eat, whales remained only moderately large creatures for millions of years.
“But suddenly we see them getting very big, like blue whales,” said Nick Benson, curator of the ancient marine mammal collection at the Smithsonian Institution's National Museum of Natural History, and one of the study's authors. “It's like going from whales the size of a pickup truck to two longer school buses.”
Dr. Pyenson and his colleagues measured more than 140 museum specimens of fossilized whales, then plugged that data into a statistical model. It showed that several distinct lineages of baleen whales became giants at about the same time, independently of each other. About 4.5 million years ago, giant blue whales appeared in oceans around the world alongside giant bowhead whales and giant fin whales.
Researchers suspected that an environmental change occurred during that period that essentially caused baleen whales to increase in size. After doing some research, they found that this time period coincided with the early beginnings when ice sheets increasingly covered the Northern Hemisphere.
Groundwater drainage from the ice sheets would have transported nutrients such as iron into coastal waters, and would have had an impact on the coast. The intense monsoon cycle will cause cold water from the depths to rise to the surface, bringing organic matter toward the surface. These environmental impacts will therefore bring with them large amounts of nutrients into the water at specific times and places, creating an interfering effect on the ocean's ecological food web.
Large amounts of zooplankton and krill aggregate to feed on nutrients, and will form dense aggregations that can extend for several miles in length and width and are more than 65 feet thick. The oceans thus become huge buffets for whales, where whales can eat huge amounts of food.
“Even though they had the anatomical machinery to filter food for a very long time, the ocean did not provide them with these incomplete resources,” said Jeremy Goldbogen, a comparative physiologist from Stanford University and an author on the paper. This makes the bulk filter feeding process very efficient.
Baleen whales can now swallow much larger amounts of prey, which has allowed them to grow larger. But that was only part of the equation.
“Plentiful food everywhere is not going to give you huge whales,” said Graham Slater, an evolutionary scientist at the University of Chicago and an author of the study. “There must be large distances between them.”
Because the ecological cycles that fuel krill and zooplankton explosions occur seasonally, Dr. Slater said the whales must migrate across thousands of miles from one feeding area to another. Their larger ancestors had larger fuel tanks, which gave them a better chance of surviving these long seasonal feeding migrations, while smaller whales became extinct.
If the feeding grounds were not some distance away, Dr Slater said the whales would grow to a comfortable body size for this environment, but they would not be the giants we see today.
“The blue whale is able to move farther using less energy than other small-bodied whales,” Dr. Slater said. “It becomes really useful if you're going to be moving long distances to have a large size.”
Ari S. said: Friedlander, a behavioral ecologist at Oregon State University who was not involved in the study, said this research advances our understanding of how baleen whales become giant whales. "What this does is it allows us to say that there were critical processes in the ocean that allowed these animals to become this size," he added.
Richard Norris, a paleontologist at the Scripps Institution of Oceanography, described the study as a "beautiful work" and said it confirmed scientists' current understanding of changes in the oceans over time.
“When we think about what the planet was like in its long history, the whale 10 million years ago was a very different type of creature than we have now,” Dr Norris said. “So, we live in a special time where we can enjoy the majesty of truly large animals found in the ocean.”
Source: nytimes
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