The 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 smaller than most baleen whales yet large among beaked whales. Cuvier's beaked whale is pelagic, inhabiting waters deeper than . It has the deepest and longest recorded dives among whales at and 222 minutes, though the frequency and reasons for these extraordinary dives are unclear. Despite its deep-water habitat, it is one of the most frequently spotted beaked whales.
The species was named Ziphius cavirostris by Georges Cuvier, based on a skull fragment which he believed to be a fossil from an extinct species. He reused the genus name Ziphius from an undetermined species mentioned by historical sources. The species name cavirostris, from Latin "hollow" and "beak", refers to a bony structure (cavity) anterior of the nares (the bones of the nose), now known as the prenarial basin. It is now known to be unique to males of this species.
Taxonomy
French naturalist and zoologist Georges Cuvier first described the species in Recherches sur les ossements fossiles ("Research on Fossil Bones", 1823) based on a skull collected on the Mediterranean coast of France at Fos-sur-mer, Bouches de Rhone in 1804. He named it Ziphius cavirostris from the Latin cavus for "hollow" or "concave", referring to the prenarial basin, a deep hollow in the skull which is now known to be found only in males of this species.
Cuvier believed the skull represented the remains of an extinct species, and chose the genus name Ziphius to reflect an undetermined species mentioned by historical authors. Later, in 1850, paleontologist and zoologist Paul Gervais found the skull to be identical with that of a whale carcass more recently stranded on a beach.
Cuvier's beaked whale is one of 22 species in the family Ziphiidae and the only member of the genus Ziphius. No other ziphiid develops the dense rostral ossification of the prenarial basin.
Description
The body of Cuvier's beaked whale is robust and cigar-shaped, similar to those of other beaked whales, and can be difficult to distinguish from many of the mesoplodont whales at sea. Males and females tend to be similar in size. The body of adult males is typically a dark gray, with their head being distinctly lighter, or even white. This light coloration extends along the posterior. Females vary in color from dark gray to a reddish-brown. The skin lightens on female's head to a lesser extent than in males, and does not extend along the posterior.
Sex determination in Cuvier’s beaked whales can be on the basis of genetics, observation of the genital area, the presence or absence of erupted teeth in adults, or presence of a calf. Pigmentation patterns can also give indications of gender. Adult males show a contrasted uniform white cape which usually extends to the dorsal fin zone. Individual coloration in adult males varies from dark to almost white. However, more than a third of adult females show "sharp" pigmentation patterns similar to adult males. Therefore males and females of this pattern cannot be distinguished using pigmentation pattern alone. The majority of adult females show a “soft” cluster of pigmentation features characterized by a brownish coloration and a shorter contrasting white cape. However, similar patterns have been observed in subadult animals of both sexes, so a "soft" pigmentation pattern alone is insufficient evidence to conclude that an animal is female.
Cuvier's beaked whales at birth have a weight about and a length of . Calves are black or dark blue with a white belly. Females reach maturity at an average length of and males at , weighing about 2 to 3.5 tons.
Cuvier's beaked whale is an odontocete — or toothed whale. Erupted teeth are only present in the adult males. Males also develop two tusks in the right and left corners of their lower jaw. The tusks are possibly used for dueling between the males, though it has not been observed, but may also be used for fighting off threats such as orcas. Adults have many scars along their sides which can be used to identify individuals. The scars are thought, by researchers, to be from battles with males, predators, fights with squid, or cookiecutter sharks, which may score them or punch holes directly in their sides. The frequency of scarring is higher in males than in females, and tends to increase with age.