Whale of the Month - Cuvier's Beaked Whale
Species fact file
Common names: Cuvier’s beaked whale, goose-beaked whale
Icelandic name: gáshnallur, skugganefja
Scientific name: Ziphius cavirostris
Family: Ziphiidae (beaked whales)
Max length: 7m
Distribution: Globally, generally in offshore waters
Cuvier’s beaked whale was first described in 1823 by Georges Cuvier, based on a skull collected on a beach in southern France. At the time, he believed it was the remains of an extinct species – it wasn’t until 1850 that the skull was matched to one taken from the carcass of a stranded beaked whale.
More is known about Cuvier’s beaked whale than most other species in this family. They are the most common of all beaked whales and also the most widely distributed; inhabiting deep waters in all oceans, from pole to pole, and in several semi-enclosed seas such as the Mediterranean. However, they are still a relatively difficult species to study due to their preference for deep offshore regions, so estimates of population size are limited and often come with a large margin of error. There are probably over 100,000 of them worldwide.
Some long-term research has been possible in oceanic archipelagos such as Hawai’i and the Canary Islands. Here, photo identification databases reveal relatively small but stable populations with limited movement into or out of the area. Social groups within these populations are typically small, consisting of at most 4 or 5 animals, and associations between individuals don’t seem to persist for long periods of time.
Like all beaked whales, Cuvier’s beaked whales are masters of the deep ocean. They hunt mainly for squid and can dive to incredible depths to do so. Cuvier’s beaked whales hold the record for the deepest and longest dives of any cetacean: 2,992m and 222 minutes (3h 42 minutes), respectively. Just like us, Cuvier’s beaked whales are mammals and they breathe air; this means that, incredibly, they hold their breath for the whole time they are underwater! This blog post explains in more detail how whales and dolphins can go without air for such long periods of time.
Because they spend so long at such depths, well out of the reach of human scientists, much of what we know about this species comes from tags. The tags attach with suction cups to the animal’s back – watch this video to see tag deployment in action! They stay on for the duration of the dive before falling off, usually after a few hours, and float at the surface until they are located with GPS and retrieved. Each tag carries sensors that collect a wealth of data, such as depth, temperature, dive time, swimming speed, and position in the water. They often have microphones built in which can provide information on echolocation and acoustic communication.
Adult males have a pair of tusks that erupt from the front of their jaw. These tusks are not used for hunting or feeding; Cuvier’s beaked whales don’t need teeth to hunt because they use a specialised technique called suction feeding. They have grooves in their throat which they can expand, creating a rapid change in pressure which sucks their prey into their mouth to be swallowed whole. Males only use their tusks in combat with other males over access to females. There is little difference in body size between the two sexes, but males can be distinguished from females by the scars on their body that result from these fights.
The greatest threat to Cuvier’s beaked whales at present is the effect of noise pollution. All beaked whales seem to be particularly sensitive to noise, particularly from military sonar. Several mass stranding events have been linked to offshore naval exercises: this was first noted in the Bahamas in 2000, but has also been reported as a potential cause of mass mortality events in Greece, the Canary Islands, Italy, Madeira, and the UK. Necropsies of the beaked whales that strand during these events reveal symptoms of DCS – decompression sickness, or ‘the bends’ – a syndrome well known to human SCUBA divers. DCS occurs because nitrogen builds up in body tissues while at depth. Upon rapid ascent, the nitrogen forms bubbles in the blood. This can interfere with blood flow, affecting the spinal cord and brain in particular, and is potentially fatal.
We still don’t know exactly how naval sonar causes DCS in beaked whales. General consensus is that exposure to such high-intensity noise triggers abnormal dive behaviour, such as extended periods at depth or a very rapid return to the surface, which then leads to DCS.
Beaked whales follow their deep foraging dives with a relatively slow ascent and either a long surface interval or a series of multiple short, shallow dives. This diving behaviour is unlike that of other cetaceans and makes them especially vulnerable to DCS. Cuvier’s beaked whales dive deeper and longer than all other whales, regularly pushing their bodies to the limits. If any part of the dive sequence is interrupted it could lead to an excess of nitrogen in the body, resulting in gas bubble formation – and potentially death.
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Photo identification of Cuvier’s beaked whales