Wet Beast Wednesday: Cuvier's beaked whale
Today's Wet Beast Wednesday post is going to be a deeper dive than usual, because this week's post is about the deepest-diving whale. Beaked whales are an elusive and poorly-understood family known for diving to extreme depths. Of the 24 known species, Cuvier's beaked whale is the most well-known. Dive in (get it?) to learn about this cryptic cetacean.
(Image: a Cuvier's beaked whale underwater. It is a small whale similar in appearance to a bottlenose dolphin, though stockier and with a shorter snout. The dorsal fin is far back on the body Its body is gray and covered in white, circular scars, likely bites from cookie cutter sharks. End ID)
Beaked whales are poorly-studied because of their remote habitats and tendency to spend more time underwater than other whales. It is also often hard to distinguish between different species without a close examination. The name comes from their skulls, which are notably toothless and elongated around the mouth, making them look like they have beaks. Beaked whales only have one pair of teeth and they only grow out in males. Female beaked whale teeth remain in the gums and never grow. Cuvier's beaked whale (Ziphius cavirostris), sometimes called the goose-beaked whale, is large for a beaked whale, with the larger males maxing out at 7 meters (23 ft) and 3.5 tons. They resemble dolphins in body shape, but with robust and stocky bodies. Their bodies are gray to light brown while the heads are lighter in color, especially in males. The melon is relatively small and the mouth is shorter than in most beaked whales, making it easier to differentiate them. The melon is an organ found in toothed whales that aids in echolocation.
(image: a beaked whale peaking its head out of the water. It is likely a male due to its white face. Its back is densely covered in long, whit scars. End ID)
Beaked whales have multiple adaptations to deep diving. During dives, the heart rate decreases and blood flow is redirected to more important organs and tissues. The lungs collapse, leaving oxygen storage to the hemoglobin in the blood and myoglobin in the muscles. Long periods of time without breathing results in the buildup of lactic acid in the blood, which can be toxic. Beaked whales have enlarged spleens and livers that may help filter lactic acid out of the blood. Their bodies are very streamlined and the flippers can be held very tightly against the body to reduce drag. There are likely other adaptations for very deep and very long dives that have not been studied.
(Image: the skeleton of a Cuvier's beaked whale. It is somewhat short for a whale, with small flippers. The skull is long and flat. End ID)
Cuvier's beaked whale is the most widely-distributed beaked whale, being found worldwide in tropical to temperate waters. They prefer to swim in very deep water and are rarely seen near shore. Cuvier's beaked whale holds the record for the deepest and longest dive of any marine mammal. The records (recorded by satellite tags) for depth was a dive to 2,992 m (9,816 ft) and for length was a 222 minute (about 3.75 hours) dive. The whales will usually make multiple shallower dives to around 500 m (1,640 ft) between each deep dive, possibly to give their bodies time to recover while still searching for food. They spend very little time at the surface between dives, usually no more than 8 minutes. These short surface intervals may be to avoid predators like orcas. Occasionally, longer surface intervals of several hours have been observed. Their hunting behavior changes depending on how deep they dive. On shallower dives, they remain silent, possibly to avoid being overheard by predators, while on deep dives, they use echolocation to find prey in the darkness of the deep ocean. Cuvier's beak whale hunts via suction. They open their mouths while retracting the tongue and enlarging the throat to create a vacuum that sucks prey into their mouths, which is then swallowed whole. Dissections have revealed that squid make up over 80% of their diet. The whales forage in small pods that coordinate their dives and hunting strategy. It has been speculated that the teeth of males are used to fight over access to females. Males have been found with scars that would seem to fit being raked with another male's teeth. Males also generally have more scars than females, which would be consistent with them fighting each other. Almost nothing is known about beaked whale reproduction, though calves do live with their mothers as in other whales.
(Image: a Cuvier's beaked whale jumping out of the water. End ID)
Little is known about the conservation needs of Cuvier's beaked whale. They are likely the most abundant species of beaked whale due to their wide distribution. They are known to be threatened by entanglements in fishing nets and have been harvested by whalers in the past. They may be targeted by the Japanese whaling industry, but it is difficult to be sure due to the secrecy of said industry. Cuvier's beaked whale is known to be vulnerable to sonar, especially mid-range sonar. They have been observed avoiding areas where sonar is used and use of sonar has been correlated to mass strandings and symptoms of decompression sickness (the bends). It is possible that the sonar drives them to ascend from dives too quickly, leading to potentially fatal gas embolisms. Notably, several mass strandings happened in the Canary Islands while naval exercises were performed there. Once those exercises stopped, the mass strandings stopped as well. Cuvier's beaked whale was described and named by naturalist, zoologist, paleontologist, and virulent racist and misogynist Georges Cuvier, who described it using a skull he thought was a fossil. There has been a small push recently to begin using the name goose-beaked whale instead to keep from honoring him.
(Image: a Cuvier's beaked whale poking its head out of the water. Its body is light gray, with a few scars. End ID)
