Why penguin poop makes krill swim for their lives
In Antarctica's Palmer Station lab, scientists put wild-caught krill through a series of tests to see if they could identify the presence of a predator—in this case, Adélie penguins—by squirting a slurry of penguin poop into the crustaceans' tanks. Because there were just six to eight individuals in each test, the scientists were then able to measure the krill's reactions.
'You could see straight away that they were having these avoidance behaviors,' says Nicole Hellessey, an Antarctic marine scientist at the University of Tasmania in Hobart, Australia and lead author of the new study published in Frontiers in Marine Science. 'They'd start to zigzag all over the place.'
More specifically, the krill swam faster, with three times as many turns—and turns at sharper angles—than usual.
Sometimes the krill would stop swimming altogether, allowing the flow of water in their holding tanks to carry them all the way to the side of the enclosure. Hellessey notes that if the current is carrying the krill away from a predator, then it saves the krill energy to just sit tight and float along with it.
Interestingly, the krill also appeared to lose their appetite in the presence of penguin poop, feeding 64 percent less efficiently than under normal conditions.
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