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Baleen whales that filter small prey, such as krill, out of seawater were then well-equipped to take advantage of these dense patches of food. As the marine mammals’ body size began to increase, their foraging became all the more efficient.
Clearly not all gigantic animals have been filter-feeders, though.
“Gigantism seems to have different causes and consequences in different lineages,” Slater said. “Whether you’re warm- or cold-blooded, what kind of food you eat, and where you live will all affect how quickly you can get big and how long you survive as a lineage. In the case of baleen whales, filter-feeding sets the table, but you need to serve the food to allow them to really take advantage.”
Blue whales today are endangered, though, and face threats from climate change, pollution and other human-related problems. The environmental stage then appears to be in place for baleen whales to evolve into smaller sizes again, but scientists are not sure if the marine mammal giants are capable of doing this, and within enough time for the reduced size to benefit their survival.
When prey patch densities reduce, baleen whales must forage to obtain enough energy, but their health may suffer as a result, Goldbogen said, referring to the whales expending more energy at times than their food intake provides.
He and his colleagues therefore wonder if the world’s oceans have the capacity to sustain both several billion people and the planet’s largest whales. If baleen whale populations continue to drop, then these icons of the oceans may very well join Megaladon and T. rex as being memorable giants of the past.
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