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The mysterious Cuvier's beaked whale is already known for its ability to dive to extreme depths, and now it has set a new record.
On Wednesday, scientists announced that the Cuvier's broke the record for the deepest and longest dive of any mammal, descending to a depth of 9,816 feet (1.86 miles) and staying under for almost 2.5 hours.
The previous record was held by the southern elephant seal, set at 7,835 feet below the ocean's surface and lasting for 120 minutes.
For the study, scientists fixed satellite tags to eight Cuvier's whales off the Southern California coast. Researchers were amazed that the tags could even operate at such extreme depths.
"Our first step after receiving the record," lead researcher Gregory Schorr from the Cascadia Research Collective said in an email to Business Insider, "was to take the same type of tag and put it in a pressure tank to independently verify that the tag would indeed function that deep and report accurate values." Lucky for them, it did!
The record-breaking dives were recorded as part of a larger study, published Wednesday, March 26, in PLOS one, to better understand how Naval sonar in the Southern California area may be related to beach stranding of these whales.
Sonar activity
More than 3,000 hours of mid-frequency sonar are broadcast each year by the U.S. navy at a training site west of San Diego. If whales are in a canyon with a sonar-transmitting ship on the deeper end, the whales will move away from the sound source. In stranding cases, that may be the beach, explains Schorr.
According to a media release, the Cuvier's makes up 69% of all marine mammal strandings associated with military sonar.
"The causal link between sonar and strandings has not been definitively identified," Schorr said, "but there has been speculation that beaked whales might be highly sensitive to sound in the same frequency band as sonar."
Based on location data, the whales were found in the sonar training range 38% of the time. However, it is still "highly likely sonar use in this area disturbs these whales," Schorr said.
Because the team has not yet matched the exact times of sonar use with the locations and behaviors of the whales, it is tough to say for sure. This will be the team's next step.
New data
Beaked whales, which make up about a quarter of all cetaceans (which includes whales, dolphins, and porpoises), are some of the most mysterious ocean mammals.
Although the Cuvier's is the most widely distributed of the beaked whales, they are difficult to study because they rarely breach the surface and inhabit deep waters far from shore.
But by tracking eight whales for up to three months each, recording a total of 3,732 hours worth of data, researchers were able to gain a bunch of new information about these elusive creatures.
For example, unlike the elephant seal, the Cuvier's does not appear to need long recovery times between deep dives, averaging less than two minutes at the surface between these dives, according to a statement.
Researchers were also "surprised by the broad variability both between and within individuals," Schorr said. Previous studies had given the impression that the whales' dive behaviors were patterned and predictable, he said.
Out of the 6,827 recorded dives, almost 17% were classified as "deep dives." These were longer dives related to foraging as determined by "the presence of echolocation clicks and/or evidence of prey chases," the authors wrote in the paper.
The rest of the dives were shorter and shallower and didn't show any signs of hunting. The purpose of these dives is still an area of speculation, Schorr said. Given the great variation between individuals, Schorr thinks the shallow dives could be associated with avoiding predators, social behavior, rest, or another unknown behavior.
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