Dives of distinction

Cuvier’s beaked whales (Ziphius cavirostris) are continuing to prove why they’re considered the superstars of the diving world, with researchers timing a record-breaking three-hour 42-minute dive.

The whales can reach depths of almost 3000 metres, with previous calculations suggesting they can be submerged for just over 30 minutes before their oxygen runs out and they resort to anaerobic respiration.

“We didn’t believe it at first; these are mammals after all, and any mammal spending that long underwater just seemed incredible,” says lead author Nicola Quick from Duke University, US.

The record-breaking dive was recorded in 2017, with a second dive lasting almost three hours.

“It may be that there was a particularly productive food patch… some perceived threat… [or] some noise disturbance that influenced these dives,” says Quick.

The discovery, reported in the Journal of Experimental Biology, came after Quick and colleagues decided to investigate how often the whales embarked on the epic dives, and how long it takes them to recover once they resurface.

However, the search for the notably shy mammal – which grows to 5-7 metres and about 2.5 tonnes – didn’t come without its challenges.

“Because the animals spend so little time at the surface, we needed calm seas and experienced observers to look for them,” Quick explains. “The average period they spend at the surface is about two minutes, so getting a tag on takes a dedicated crew and a manoeuverable vessel.”

The brief surfacing time also means there’s a limited time window to transfer the information to a satellite each time the animals resurface from a dive. 

The team succeeded, however, and over a five-year period deployed 23 tags, recording more than 3600 foraging dives. The dives ranged from 33 minutes to over two hours; all of which exceeded the point it was predicted the animals would run out of oxygen.

With this data, the researchers re-visited the diving abilities of other marine mammals, which led to a new estimate for the time a Cuvier’s beaked whale can spend submerged before they resort to anaerobic respiration of 77.7 minutes.

“It really did surprise us that these animals are able to go so far beyond what predictions suggest their diving limits should be,” says Quick.

Quick and colleagues suggest the whales may have an exceptionally low metabolism, paired with larger than usual oxygen stores and the ability to withstand the stinging lactic acid build up in their muscles when they switch to anaerobic metabolism.

The team also discovered there was no clear pattern in the whale’s recovery from the dives. One whale resumed diving for food within 20 minutes of a two-hour dive. Another spent almost four hours making shorter dips following a 78-minute dive.

Previous studies have suggested a slow ascent and longer time spent in shallow water may counteract lactate buildup and mitigate decompression sickness.