Interesting Creatures... The Clymene dolphin (Stenella clymene)

Interesting Creatures… The Clymene dolphin (Stenella clymene)

Aug 09, 2015 Features / Columnists, Interesting Creatures in Guyana

The Clymene dolphin (Stenella clymene), formerly known as the short-snouted spinner dolphin, is endemic to the Atlantic Ocean. It is the only confirmed case of hybrid speciation in marine mammals, descending from the spinner dolphin and the striped dolphin.

The Clymene dolphin was first formally described by John Edward Gray in 1846, although, unusually, he did not assign it its current name until four years later, in 1850. From then on, until a reassessment in 1981, the Clymene dolphin was regarded as a subspecies of the spinner dolphin (Stenella longirostris).

In 1981, Perrin et al. asserted the Clymene’s existence as separate species. Until this time, because Clymenes are relatively remote and were regarded as very similar to the more accessible spinners, they were never heavily studied.

Anatomical and behavioral traits suggested that this species is a hybrid of the spinner dolphin (Stenella longirostris) and the striped dolphin (Stenella coeruleoalba), and DNA testing has shown that it is indeed a hybrid species.

The common and scientific names are probably derived from the Greek oceanid Clymene, although it has also been argued that it may instead come from the Greek word for “notorious”.

The Clymene dolphin looks very similar to the spinner dolphin. At close quarters, it is possible to observe that the beak of the Clymene is slightly shorter than that of its relative. The dorsal fin is also less erect and triangular.

The basic colour of the Clymene dolphin is “cetacean neapolitan” – it occurs in three shaded layers — the underside being white. Next, a strip of light grey runs from just above the beak, round either side of the eye back to the tail stock, where the band thickens. The top layer, from the forehead, along the back to the dorsal fin, and down to the top of the tail stock, is a dark grey. The beak, lips, and flippers are also dark grey in colour.

Clymene dolphins grow to about 2 m (6.6 ft) in length and 75 to 80 kg (165 to 176 lb) in weight. They spend most of their lives in waters over 100 m (330 ft) in depth, but occasionally move into shallower, coastal regions. They feed on squid and small schooling fish, hunting either at night, or in mesopelagic waters where there is only limited light. Predators include cookie-cutter sharks, as evidenced by bite marks seen on a number of animals.

Clymenes are fairly active dolphins. They do spin longitudinally when jumping clear of the water, but not with as much regularity and complexity as the spinner dolphin. They will also approach boats and ride bow waves. Group sizes vary from just four up to around 150 individuals, although about 40 is typical. Many of these groups appear to be single-sex, and also to be segregated by the approximate age of the individuals.

Clymene dolphins are also highly vocal, making short whistles in a range of 6–19 kHz.

No figures are available for the size of animals at birth. Gestation, lactation, and maturation periods are all unknown, but are unlikely to vary greatly from others in the Stenella genus. Their longevity is also unknown, although at least one sixteen-year-old individual has been reported from a stranding.

(Source: Wikipedia – the Free Online Encyclopedia)