The body shape is typically porpoise-like, but the dorsal fin is large and rounded. In at least some adult males, it becomes extremely large – so much so as to look disproportionate to the body. The flippers are small, with rounded tips.
The two-tone color pattern of spectacled porpoises is very distinctive. Above a line that runs down the side at the level of the eye, they are black (except that the line extends upward at the tail stock, just before the flukes). Below this line, they are white, with the exception of black lips and a dark gape-to-flipper stripe (the latter is apparently not present on all adults). There is a black patch, surrounded by a fine white line, around the eye. The flukes are black above and white below; the flippers are variably colored, either all dark or grayish-white with gray edges. Young animals have muted gray patterns.
Inside the mouth are 17-23 (upper) or 17-20 (lower) spade-shaped teeth in each row.
Although few specimens have been measured, adult male spectacled porpoises reach lengths of at least 2.3 m (length at puberty is unknown) and adult females are up to about 2.1 m. They can reach weights of at least 115 kg. Newborns are probably about 1 m.
Can be Confused With
The spectacled porpoise is not likely to be confused with other species, when seen well. But at a distance, there can be some confusion with Commerson’s dolphin and Burmeister’s porpoise, which both share portions of its range. These three species can best be distinguished by dorsal fin shape and color pattern differences.
Known primarily from the southern coast of eastern South America, from Uruguay to Tierra del Fuego, this species is apparently also found around offshore islands in the Southern Hemisphere. There are records from the Falkland Islands, South Georgia, Kerguelen Islands, Heard Island, Macquarie Island, and the Aukland Islands. Although rarely seen at sea, this information suggests that the spectacled porpoise may be circumpolar in the subantarctic. Sightings have occurred in offshore waters as well as in rivers and channels.
Ecology and Behavior
In the few known sightings, group sizes were small, apparently mostly singles, pairs, or trios. These animals are very inconspicuous when surfacing and do not ride bow waves.
Births appear to occur in the southern spring to summer. Essentially nothing else is known of this species’ behavior and biology.
Feeding and Prey
Only four stomachs have been examined, and the contents included anchovies, stomatopods, and a small amount of algae (the latter probably ingested incidentally).
Threats and Status
Not much is known about the status of this species. However, like all phocoenoids, spectacled porpoises are caught in gillnets. At least one record of a capture in a midwater trawl is also known. In the past, this species was apparently harpooned by Tierra del Fuegan natives, as well as fishermen and whalers. Currently, spectacled porpoises are listed as ‘Data Deficient’ (IUCN) and ‘Not Listed’ (ESA).
Brownell, Jr., R.L. and P.J. Clapham. 1999. Spectacled porpoise Phocoena dioptrica Lahille, 1912. pp. 379-392 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 6: The second book of dolphins and the porpoises. Academic Press.
Goodall, R.N.P. 2002. Spectacled porpoise Phocoena dioptrica. pp. 1158-1161 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Jefferson, T.A. and B.E. Curry. 1994. A global review of porpoise (Cetacea, Phocoenidae) mortality in gillnets. Biological Conservation 67:167-183.
Perrin, W.F., R.N.P. Goodall and M.A. Cozzuol. 2000. Osteological variation in the spectacled porpoise (Phocoena dioptrica). Journal of Cetacean Research and Management 2:211-215.
Rosel, P.E., M.G. Haygood and W.F. Perrin. 1995. Phylogenetic relationships among the true porpoises (Cetacea Phocoenidae). Molecular Phylogenetics and Evolution 4:463-474.