Cuvier Beaked Whale takes gold for deepest diving marine mammal
In 2013 the Cuvier’s beaked whale set the record for deepest and longest lasting dive, clocking in at a staggering 2 hours 17 minutes, reaching a record breaking depth of 2,992m (1.9 miles). This is the equivalent of 3 and a half of the world’s tallest building, The Burj Khalifa in Dubai, stacked on top of one another.
The true potential of this whales diving capabilities was revealed when biologist Erin Falcone and her team of researchers from Cascadia research collective began the study using a set of advanced satellite tags. These advances in technology enabled the team to collect data on the whales diving patterns for the first time. The team collected over 3,700 hours of diving data during this study, with information covering 1,000 individual deep dives. 8 Whales were tagged in total in the Southern California Anti-Submarine Ware-fare range displayed and outlined in white below. The mean group depth of the whales studied was 1,401m, with a mean duration of 102.3 minutes. However the whale in question surpassed all others taking these marine mammals to victory for the deepest and longest diving marine mammal to ever exist.
The record breaking dive of the Cuvier’s, reported in the journal Plos One, knocked the southern elephant seal of the top spot which previously held the position as the marine mammal with the longest and deepest dive on record, which was documented at a depth of 2,388 metres. A Separate study in 1992 found they can dive for a 2-hour duration. The tagging data revealed that the diving behaviour carried out by the whales had a trend, a single deep foraging dive followed by a series of shallow dives, does this mean these mammals can navigate their way through the water column with relatively little trouble?
The Cuvier’s beaked whale Ziphius cabirostris, also referred to as the goose-beaked whale, is the only member of genus Ziphius. These whales have a Cosmopolitan distribution commonly found in deep offshore waters ranging from the tropics including the Mediterranean sea, to cooler oceans in the North Atlantic. It grows between approx. 5-7m, and weighs in at 2,500kg. Its dorsal fin is small, curved and located two thirds of the way down its body and It’s flippers are small, narrow and tuck into pockets In the body wall, thought to be adapted for improved hydrodynamics. As well as this, they have a large fluke and a gently sloping bulbous melon, more so than any other species of beaked whale.
So how do they adapt to the deepest depths of the ocean?
Pressure increases about one atmosphere for every 10 metres of water depth. At a 3,000 metres depth that will be approximately 300 atmospheres, or 300 times greater than pressure at the surface. So what does their biology tell us? The Cuvier’s beaked whale is extremely flexible and possesses a bendable rib cages made up of cartilage that can fold down, enabling them to collapse their lungs emptying them almost entirely of gas. As well as this, in deep diving whales the size of their lungs is relatively small compared to body size and in fact only takes up 3% in total, comparing that to a human being whose lungs take up 7% of total body size ultimately meaning in relation to body size, your lungs are larger than a deep diving whales. This ensures the lungs of the animal don’t act like a balloon, pulling them back up to the surface. Before diving, these animals are also known to exhale 90% of the air in their lungs giving them negative buoyancy making it easier to sink. However, with little air, this leaves the whale facing a whole new problem, they must conserve enough oxygen to sustain the long duration they will be submersed. In order to do this, it has been found these expert divers divert blood flow from their extremities to the heart, brain and muscles. They also completely shut down digestion, kidney and liver function.
Lastly, they lower their heart rate, and prohibit movement to preserve oxygen, allowing them to glide down to the deepest depths, aided by their shrinking lungs mentioned. This is all good and well reaching their final destination, however Cuviers beaked whales feed on fast moving squid, so they needed to come up with a way of producing oxygen to fuel their hunt. To do this, they have been found to preserve high amounts of oxygen in their muscles post lung collapse due to the high levels of haemoglobin and positively charged myoglobin which is 10 times more concentrated in the muscles of diving animals than in human muscles. This allows them to breath less frequently whilst remaining relatively active.
This video shows University of Liverpool’s Dr Michael Berenbrink explaining how marine mammals are able to hold their breath for so long using myoglobin.
Why travel so deep?
Cuvier’s Beaked Whales, much like the sperm whale Physeter microcephalus, dive to hunt for prey. It is also thought they dive to avoid being hunted themselves. They have predators such as killer whales which present a threat to beaked whales in shallower waters. The payback in terms of food sources must be worth the risk, as these whales face many at these deep depths. In 2002 when 14 beaked whales were found stranded on a beach in the canary islands, an autopsy was performed by a group of scientists from the institute of zoology in London were they found severe haemorrhages associated with pockets of gas in vital organs, showing evidence for the first time that whales can get the bends.
This relatively new discovery has shown how little we know about deep diving whales, due to the limitations of monitoring beaked whales in-situ because they spend so little time at the surface. This discovery has shown us that the Cuvier’s beaked whale is well adapted for regular deep dives into the abyss, but we are uncertain of how well due to evidence of the bends. By learning more using the latest technological advances to monitor these beaked whales, we may gain a better understanding on how far these whales will push themselves, and whether the benefits out weigh the risks.