Baleen whales are remarkably skilled at navigating the vast oceans during both epic migratory journeys and day-to-day hunting and foraging expeditions without getting lost. We’re still not quite sure how they do it, and our best guess up until the 1990s was that they use a combination of cues from the position of the Sun, stars, and Earth’s magnetic field. Recent evidence suggests that the filter-feeding giants actually use echolocation as well, just like their smaller-toothed whale cousins, orcas and dolphins; shifting the previous belief that vocalizations were used for communication purposes only.
Now, we have to further reconsider the importance of sound for these animals.
A group of marine scientists from Oregon State University propose that whales may use the noise generated by snapping shrimp to hone in on areas rich in zooplankton, their primary food source.
The team were recording underwater sounds off the northern Oregon coast as part of ongoing research into the effect on whales of human-generating sound pollution. In addition to the expected grumble of boat engines and sonar, cetacean calls, and swirling water, an outright cacophony of crackling was picked up.
“We brought the data back and started looking through it, and we found an area where there wasn’t a lot of boat traffic and we knew there wasn’t a lot of weather, we had this really loud signal happening,” said OSU geophysical acoustics professor Joe Haxel at the 2018 Ocean Sciences meeting happening this week in Portland.
The distinctive sound could belong to only one organism: The snapping shrimp.
Species of this crustacean family are found throughout tropical and temperate coastal waters, but none had ever been observed this far north. Also known as pistol shrimp, the creatures are famous for their out-of-proportion claw that can snap with such great speed that a shock wave capable of stunning or killing significantly larger prey – or breaking the glass of an aquarium tank – is created.
After noticing that the shrimp and large clusters of zooplankton are found together in rocky, shallow-water areas, Haxel hypothesizes that hyper-intelligent whales have likely realized the same.
“We’re starting to explore the idea that maybe the snapping shrimp could provide an acoustic cue for the gray whales as they’re foraging. That this may be an area of more prey," said Haxel.
Should this turn out to be true, it will be added to the list of horrifying effects that boat noises are known to have on marine mammals. According to Oregon Public Broadcasting, the only thing loud enough to cover the dinner alarm of snapping shrimp is passing boats.
[H/T: Oregon Public Broadcasting]