Blue whales, the largest animals on Earth, can eat about four tons of food a day—and when they’re done digesting, there’s still a whole lot of stuff left over. This aerial shot, taken by oceanographic consultant Eddie Kisfaludy off the Southern California coast, shows a blue whale and a truly enormous plume of its poop, the same vibrant orange as the krill on which the whales feed.
Whale feces, it turns out, plays a substantial role in ocean ecosystems. Since it floats to the surface, it brings nitrogen whales have taken in when they fed in the ocean’s depths to shallow waters, providing a much-needed nutrient for plankton there. The massive mammals’ poop also serves as a significant carbon sink; one study estimated that excrement from sperm whales in the Southern Ocean alone sequestered 400,000 tons of carbon dioxide a year.
It takes a tremendous amount of energy to move the largest animal on Earth from a standstill to chasing food in a fierce dive. Could the krill that a blue whale catches in its gargantuan mouth really provide a high enough calorie count to make all this effort worthwhile? To find out, Jeremy Goldbogen tagged whales with data recorders and monitored hundreds of their dives. It can take 770 to 1900 calories to get the whale moving, but it’s worth it.
When Goldbogen plugged the data from his recorders into a simulation of a feeding whale, he found that the lunge is staggeringly efficient. Despite the massive outlay in energy, the whale easily recoups anywhere from 6 to 240 times that amount, depending on how big it is and how tightly packed its krill targets are.
If a big whale attacks a particularly dense swarm, it can swallow up to 500 kilograms of krill, eating 457,000 calories in a single monster mouthful and getting back almost 200 times the amount it burned in the attempt. A smaller whale lunging at a sparse collection of krill would only get around 8,000 calories, but that’s still 8 times more than what it burned. Even when Goldbogen accounted for the energy needed to dive in search of prey, the whales still regained 3 to 90 times as much energy as they spent.
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Image: Wikimedia Commons