DURHAM, N.C. – It was a whale of a dive.
In 2017, a Cuvier’s beaked whale that had been tagged by a team of Duke University marine scientists dove deep into the waters off Cape Hatteras, N.C, and stayed below the surface for 3 hours and 42 minutes before coming up for air – making it the longest whale dive ever recorded.
That same year, it also did another dive lasting nearly 3 hours, the second-longest dive ever recorded.
“Cuvier’s beaked whales are extraordinary divers, but these dives far exceeded anything we’d seen to date,” said Nicola Quick, a marine biologist at the Duke University Marine Lab, who led the study.
The new record is about seven times longer than scientists previously thought the deep-diving but mammals were capable of, based on their body size and metabolic rate.
Quick and her colleagues at Duke and the Fundación Oceanogràfic de la Comunitat Valencia in Spain published their data on the dives in a peer-reviewed study Sept. 23 in the Journal of Experimental Biology.
Though the two record-shattering dives provided an unexpected exclamation point to the new study, the scientists’ main purpose in conducting the research was to learn how the whales – which are known to dive to depths of nearly 10,000 feet – can stay submerged for so long, and how long it takes their bodies to recover after a dive.
Notoriously boat-shy, Cuvier’s beaked whales spend little time at the surface, making them challenging to tag and study.
Previous calculations have estimated that the whales, which can grow to around 5,000 pounds and 20 feet long, should be able to store enough oxygen to sustain dives of 33 minutes.
By analyzing data from more than 3,600 dives by two dozen whales tagged between 2014 and 2018, Quick and her team discovered that the animals are actually capable to remaining submerged for nearly 78 minutes, on average, before their oxygen reserves run low and they resort to anaerobic respiration.
“It really did surprise us that these animals are able to go so far beyond what predictions suggest their diving limits should be,” Quick said.
Equally surprising was that recovery times varied significantly and didn’t seem to determined by the duration a dive.
While one whale resumed diving for food within 20 minutes of a two-hour dive, another that had completed a 78-minute dive spent nearly four hours making shorter dips and returning to the surface for air before initiating its next deep dive for foraging.
“Going into the study we thought that we would see a pattern of increased recovery time after a long dive. The fact that we didn’t opens up many other questions,” said Quick.
She and study co-author Andreas Fahlman of the Fundación Oceanogràfic de la Comunitat Valencia hypothesize that the animals may have an exceptionally low metabolism, coupled with larger than usual oxygen stores and the ability to withstand the painful buildup of lactic acid that occurs in their muscles when they switch to anaerobic metabolism after dive durations exceed the 77.7-minute mark, but further research is needed to know for sure.
As for those two record-breaking dives? Quick believes though they were remarkable, they probably pushed the very outer imit of the animal’s physical capabilities and are not typical for the species.
“It may be that there was a particularly productive food patch, some perceived threat or some noise disturbance that influenced these dives,” she said. Both dives occurred just weeks after marine mammals in the area were exposed to a Navy sonar signal, a noise that numerous past studies have shown can disorient and disturb many marine species.
Quick and Fahrman’s coauthors on the study were Jeanne Shearer and William Cioffi, both doctoral students at Duke’s Nicholas School of the Environment, and Andrew J. Read, Stephen A. Toth Professor of Marine Biology and director of the Duke Marine Lab.
Funding for the study came from the U.S. Fleet Forces Command through the Naval Facilities Engineering Command Atlantic.
CITATION: “Extreme Diving in Mammals: First Estimates of Behavioral Aerobic Dive Limits in Cuvier’s Beaked Whales,” N.J. Quick, W.R. Cioffi, J.M. Shearer, A. Fahlman and A.J. Read; Sept. 23, 2020, Journal of Experimental Biology. DOI: 10.1242/jeb.234187