Since the mid-1990s, the common dolphin has been split into two species, the long-beaked common dolphin and the short-beaked common dolphin (2) (4). As implied by their respective names, beak length is important for distinguishing between the two species, but is not the only defining feature (2). Based on specimens from California, both species have a bold, light and dark hour-glass pattern on the side of the body, forming a V below the dorsal fin, but the colouration of the long-beaked species is noticeably muted. A slightly curved dorsal fin is equally characteristic of both species but the body of the long-beaked common dolphin is more slender and the head is less rounded (2) (5). The long-beaked dolphin has more teeth than any other dolphin with 47 to 67 pairs lining each jaw (6).
Although an exceptionally long-beaked form occurring in parts of the Indo-Pacific is sometimes considered to be a separate species, the most recent evidence indicates that it is a subspecies of the long-beaked common dolphin, Delphinus capensis tropicalis (1) (4) (7).
There is growing evidence that several scattered populations, currently labelled as long-beaked common dolphins, may have actually evolved independently of each other in response to similar ecological conditions. The implications of this convergent theory are that these populations potentially represent different subspecies of the short-beaked common dolphin, or even unique species. Supporters of this alternative taxonomic view point to the fact that, in parts of the long-beaked common dolphin’s described range, it is very difficult to separate the two species of common dolphin on either morphological or genetic grounds (8). Needless to say, more research is needed before the true taxonomic status of this species will be revealed (9).
- Dauphin Commun A Bec Large.
- Delfín Común A Pico Largo.
- Male length: 2 - 2.6 m (2)
- Female length: 1.9 - 2.3 m (2)