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Despite their enormous size, blue whales rely on a small shrimp-like creature called krill to survive. And krill also dictates when the large animals feed, a new study suggests.
Researchers from NOAA’s Fisheries, Oregon State University and Stanford University, found that the majestic animals carefully plan when to eat based on the density of krill patches. They sometime reach the conclusion that the patch is not dense enough to worth the effort.
Scientists explained that blue whales consume enormous amounts of energy while feeding, so they need to make sure that the effort pays off. If krill isn’t plenty in an area, wasting energy may lead to unnecessary weight loss.
The new findings challenge previous belief that the large marine mammals engage in mindless foraging sessions whenever they see a krill patch in sight. A single patch can contain about 2 million small sea creatures but not all patches have the same density. And blue whales need about 4 million krill per day to maintain their impressive body size.
Study authors said that when a blue whale feeds, it accelerates, open its mouth and engulfs as much sea water as its own body mass or more. The whale’s throat muscles relax to allow the water come in and quickly contract to force the water out and sieve the prey through the animal’s baleen plates.
Blue Whales have hundreds of these baleen plates which hang from their upper jaw. The plates are very dense so they act like a sieve for the krill in sea water. The whale pushes water and prey towards the plates with help from its tongue which can weigh as much as an adult elephant.
Adult blue whales can outweigh two dozen adult elephants and they grow as large as a basketball court.
Elliott Hazen, one of the authors of the study and researcher with NOAA’s Fisheries, noted that blue whales optimize their feeding behaviors, rather than simply opening their mouths when they are hungry. The mammals are efficient foragers, not mindless grazers.
Blue whales also have a tactics that allows them to eat more krill. When they hunt in group they dive below the krill patch and create a fountain of bubbles to disorient their prey. The displaced patch is then a lot easier to capture.
The research team monitored more than a dozen blue whales during their study and learned that the large animals are extremely attentive to krill population density before opening their mouths to feed. If krill is scarce they lunge fewer times every dive so they save precious energy and oxygen.
Image Source: Antarctica.gov
