Cuvier's beaked whale, goose-beaked whale, or ziphius (Ziphius cavirostris) is the most widely distributed of all beaked whales in the family Ziphiidae. It is among the largest beaked whales but smaller than most baleen whales, reaching lengths of about 4.5–7 m (15 to 23 ft) and weights of 1,800–3,100 kg (4,000 to 6,800 lb).
This species is pelagic, meaning it inhabits deep offshore waters far from coastlines, typically deeper than 1,000m (3,300 ft).
Cuvier's beaked whales hold the record for both the deepest and longest recorded dives among mammals. Recorded dives have reached depths of 2,992 m (9,816 ft) and durations of 222 minutes.
Although the species is currently listed as Least Concern by the International Union of Conservation of Nature, it faces several anthropogenic (human-made) threats, including entanglement in fishing gear, hunting, and ocean noise. Adult Cuvier beaked whales vary in length from 15–23 ft and weight from 4,000–6,800 lbs.
Coloration varies between individuals and sexes. Adult males are typically a dark gray over most of their body, with the head being slightly lighter grey or even white. Females vary in color from dark gray to a reddish-brown, and their head lightening is usually less pronounced.
Adult males often bear numerous scars along their bodies. These marks can be used to identify individuals. The scars are believed to be from battles between other males, as well as interactions with predators, such as cookiecutter sharks and lampreys.
Head and facial anatomy
Their head is relatively short and blunt compared with other beaked whales. The forehead slopes gradually toward a small, poorly defined beak (rostrum). In profile, the species' rostrum gives it a goose-like appearance, which is the origin of the alternative name of "goose-beaked whale". Like other toothed whales, it has a melon, a rounded structure of fatty tissue in the forehead that helps focus echolocation sounds used for navigation and hunting.
Teeth
Cuvier's beaked whale is an odontocete (toothed whale). However, visible erupted teeth are only present in the adult males. Males also develop a pair of tusk-like teeth in the right and left corners of their lower jaw.
Lifespan and reproduction
thumb|A pod swimming off [[Dominica.]]
Newborn calves are approximately 2–3 m (6.5–9 ft) long and weigh about 250–300 kg (550–660 lb) at birth. Calves are typically black or dark blue with a lighter underside. The population in the Gulf of Mexico is extremely small and appeals have been made to have them made a protected species in this area. As of 2019 this was rejected on the basis that there was insufficient scientific evidence to consider them a Distinct Population Segment (DPS) under the Endangered Species Act (ESA).
Behavior
thumb|A whale breaching in [[Bay of Biscay]]
Diving
Cuvier's beaked whales are among the deepest diving marine mammals and spend much of their time underwater searching for prey. Satellite-linked tags and time-depth recorders have been used to track and study whale movement, showing that the species follows a relatively consistent dive pattern consisting of deep forging dives followed by several shorter dives near the surface.
Typical dives
Typical foraging dives exceed depths of 800 m (2,600 ft) and generally last between 30 and 90 minutes. After completing a deep dive, whales usually perform a series of several shorter, shallower dives before undertaking another deep dive.
Surface intervals between dives are usually brief, often only lasting a few minutes. This limited time at the surface may reduce risk of predation from its predators such as orcas and large sharks.
Record dives
Cuvier's beaked whales hold the records for both the deepest and the longest dives ever documented for any mammal. In 2014, researchers recorded a dive of 2,992 m (9,816 ft) off the coast of California.
A later study in 2020 reported Cuvier's beaked whale making a dive that lasted 222 minutes, the longest dive ever documented for any mammal.
Food and foraging
Cuvier's beaked whales primarily feed on deep-sea animals and are specialized hunters of squid. Their diet consists mainly of squid, along with deep-sea fish and some crustaceans. They usually make their dives in small social groups. Such behavior may reduce predation risk.
Echolocation is used to detect prey in deep, dark waters where sunlight does not reach. As previously stated, the "melon" of the whale, the bump on top of its head, contains its organ for echolocation. This allows them to hunt effectively at great depths and may reduce competition with other marine predators for their prey.
Most information about their diet comes from the analysis of stomach contents of stranded individuals. Examining Pacific Ocean whales, they found that cephalopods made up 98.0% (by number) and 87.7% (by mass) of Cuvier's beaked whale diet. Among these were at least 37 varieties of squid, of many different sizes. Diet can vary by region, depending on the availability of prey at different ocean depths.
Interactions with humans
Whaling and fishing
Cuvier's beaked whales have been hunted in small numbers, mainly in Japan. Before 1955, it is estimated that Japanese whalers caught anywhere from 3 to 35 Cuvier's every year. From 1955 until the 1990s, more than 4,000 Cuvier's beaked whales were reportedly caught.
In addition to intentional hunting, Cuvier's beaked whales are sometimes accidentally caught in fishing gear as bycatch, the unintended capture of animals in fishing equipment. Bycatch has been reported in regions worldwide, including the Eastern Pacific, North Atlantic, Mediterranean Sea, and parts of the Western Pacific and Southeast Asia. Most documented bycatch of Cuvier's beaked whales comes from the late 20th century, however, occasional incidents continue to be reported today. Cuvier's have been observed in Hawaii avoiding diving for food or avoiding an area where sonar is in use. A higher incidence of strandings has been recorded in noisy seas such as the Mediterranean and multiple mass strandings have occurred following operations by the Spanish Navy in the Canary Islands.
In 2019, a review of mass stranding events concluded that mid-frequency active sonar can strongly affect Cuvier's beaked whales, although responses vary between individuals, sometimes depending on their prior exposure to sonar. The study found that stranded whales often showed signs of decompression sickness and gas embolism (gas bubbles block blood vessels), likely caused by abnormal diving behavior in response to sonar. No more mass strandings were recorded in the Canary Islands once naval exercises using sonar were banned there. It was suggested the ban be extended to other areas such as the Mediterranean, where mass strandings continue to occur.
Taxonomy
thumb|left|Skull of Cuvier's beaked whaleCuvier's beaked whale was first described in 1823 by French naturalist and zoologist Georges Cuvier; he based his description on a skull found along the Mediterranean coast of France. He named the species Ziphius cavirostris from the Latin cavus meaning "hollow beak", referring to a deep hollow in the skull, known as the prenarial basin.
At the time, Cuvier believed the skull belonged to an extinct species. However, in 1850, paleontologist and zoologist, Paul Gervais, found the skull to be identical to that of a stranded (beached) whale carcass he had just examined.
Cuvier's beaked whale is one of over 20 living species in the family Ziphiidae. Males of this species have a distinctive feature: a dense, hardened area in the front part of the skull (rostrum), which is not as developed in other beaked whales.
Conservation status
Cuvier's beaked whale is classified as Least Concern by the International Union for Conservation of Nature (IUCN), meaning it is not at high risk for extinction.
The species is also covered in Annex II of the Protocol for Specially Protected Areas and Wildlife (SPAW). This is a regional agreement, that participating countries in the Greater Caribbean work together to manage and conserve listed species.
Internationally, the species is protected under agreements such as Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), covering not extinct species that could become extinct without such trade controls.
Conservation efforts mainly focus on reducing human impacts to protect biodiversity and ecosystems. Continued research and monitoring are important for better understanding the populations of species and potential risks that could threaten them further.
See also
- List of cetaceans