A new study provides the first record of the diving behaviour of Cuvier's beaked whales in US Atlantic waters.
Biologists knew the beaked whale species dove to ear-popping depths, but the new Duke University-led study offered the first in-depth documentation of the species' diving behaviour in the Atlantic.
Cuvier’s beaked whales (Ziphius cavirostris) are the world’s deepest-diving mammal, but studies of their behaviour are constrained by the animals’ offshore location and limited time spent at the surface.
Cuvier's beaked whales have one of the widest distributions of all the beaked whales and can be found in all the world's oceans and even some semi-enclosed seas. Group sizes are small (perhaps 2-7 animals), but lone animals are often seen. Little is known about the animal's social habits. Cuvier's do not bow-ride but will occasionally breach.
The elusive whales spend so little time at the surface and rarely venture close to shore, studying their behaviour very is difficult. "They typically only spend about two minutes at the surface between dives," Jeanne Shearer, a doctoral student in ecology at Duke University
The new data, recorded from 5,926 dives of tagged whales off Cape Hatteras, N.C., showcases the remarkable diving abilities of these animals and provides new clues to how they make a living at the extremes of depth and cold.
“Their deep dives average about 1,400 meters, lasting about an hour, while they are feeding near the sea floor. “It’s amazing that they can dive to such depths, withstand the pressure, and be down there that long, with such brief recovery times.”
Past studies have documented the diving behaviour of Cuvier’s beaked whales in Pacific waters, Italy, and the Bahamas, but this is the first one focused in the U.S. Atlantic. Scientists estimate about 6,500 Cuvier’s beaked whales live in the northwest Atlantic. Populations in different areas exhibit some differences in diving behaviour, highlighting the need for data from around the world.
To conduct the study, scientists attached LIMPET satellite-linked tags to 11 Cuvier’s beaked whales that live and dive most of the year in waters a two-hour boat ride from Cape Hatteras. One tag failed, but the other 10 recorded 3,242 hours of behavioural data from 5,926 individual dives — both deep and shallow — between 2014 and 2016.
Aside from the extremely deep dives that these whales are able to make, the data showed that they dive nearly continually, with deep dives followed by 3-4 shallow dives that extend to around 300 meters. How they continuously dive to these depths without long recovery periods is still a mystery to scientists.
“Cuvier’s beaked whales are only half the size of the sperm whale,” Shearer said. “Their dives push the limits of mammalian physiology, but we still don’t know how they’re able to behave this way.”
She and her colleagues published their peer-reviewed findings Feb. 6 in the journal Royal Society Open Science.
Better understanding the behaviour and movement patterns of marine mammals can help researchers more accurately predict how sonar systems and shaping traffic will impact vulnerable species.
Source: Materials provided by Duke University. Note: Content may be edited for style and length.