Phocoena dioptrica, Lahille, 1912

3. View Plate 28: Phocoenidae

Spectacled Porpoise

Phocoena dioptrica View in CoL

French: Marsouin a lunettes / German: Brillenschweinswal / Spanish: Marsopa de anteojos

Other common names: Spectacled Dolphin

Taxonomy. Phocaena dioptrica Lahille, 1912 ,

Argentina, Buenos Aires, “capturado en Punta Colares, cerca de Quilmes.”

This species is monotypic.

Distribution. Southern Hemisphere (E South America from S Brazil to Tierra del Fuego, Falkland Is (= Malvinas), South Georgia Is, Kerguelen Is, Heard I, Macquarie I, Auckland Is, and Tasmania).

Although previously thought to be exclusively coastal, like other members of the genus, recent sightings in oceanic waters of the Antarctic and subantarctic zones suggest that the species actually has a circumpolar distribution and may be largely oceanic. View Figure

Descriptive notes. Total length 150-224 cm; weight 50-115 kg. Spectacled Porpoises are relatively large members of the genus, reaching total body lengths of 224 cm for males and 204 cm for females. Males are larger than females and also have much larger dorsal fins, which become oval-shaped and proportionately very large. Leading and trailing edges of dorsalfins are both convex. Females and young have dorsal fins more typical in size and shape for the genus. There is only a slight or no beak, and flippers are small, with rounded tips. Color patternis striking, two-tone black and white. Dorsal surface and upper sides are black, and belly and lowersides are white. Boundary between the two is very distinct and runs along flanks. A white “spectacle” surrounds each eye. There are black lip and eye patches, and several dark stripes from the gape that run toward the flipper. A faint gray post-dorsal fin saddle may be visible in good lighting. Newborns have a much paler dorsal surface than adults. Tooth counts generally are 17-23 in each half of each jaw.

Habitat. Variable habitats, including very deep, oceanic waters, but also in some rivers and turbid channels near shore. Spectacled Porpoises appear to prefer cold waters, with temperatures of 1-10°C, but in fact,little is known of the ecology ofthis elusive species. The southernmost sighting of Spectacled Porpoisesis currently 64° 34” S.

Food and Feeding. Only a very small handful of stomachs from Spectacled Porpoises have been examined, so very little is understood about their feeding habits or preferences. From what is known, they appear to be opportunistic, feeding on prey items ranging from anchovies ( Engraulis ) and other small schooling fish to stomatopods and even algae (although the latter items may have been ingested incidentally just before stranding).

Breeding. There is no specific information available for this species, but births appear to occur primarily in spring and summer.

Activity patterns. Numbers of live sightings of Spectacled Porpoises at sea are very limited, and all of these have been opportunistic, so not much is known about their activity patterns. They have inconspicuous surfacing patterns and generally do not ride bow waves or leap clear of the water, although they have been enticed to occasionally surface quickly alongside the bow of research vessels.

Movements, Home range and Social organization. Groupsizes of Spectacled Porpoises are generally small, usually singletons, pairs, and trios. Occasionally groups of up to five individuals have been observed. Mother—offspring pairs are usually seen in the company of at least one attending adult male, and this may be suggestive of a mateguarding mating system, as is observed in Dall’s Porpoise ( Phocoenoides dall ).

Status and Conservation. CITES Appendix II. Classified as Data Deficient on The [UCN Red List. Just like virtually everything else about the Spectacled Porpoise, little 1s known of its conservation status. There are no estimates of abundance, and virtually nothing is known about its population structure. The first-ever molecular work on the Spectacled Porpoise indicated a large population off Tierra del Fuego. Some individuals are caught in gillnets when in coastal waters, and there is a record of an individual caught in a mid-water trawl net. They were sometimes harpooned,at least in the past, by Native Fuegians and whalers. The Spectacled Porpoises is not considered endangered or threatened at this point.

Bibliography. Best (2007), Curry et al. (1994), Evans, K. et al. (2001), Goodall (1995, 2009c), Goodall & Schiavini (1995), Olavarria (2006), Perrin et al. (2000), Pimperet al. (2012), Pinedo et al. (2002), Rosel et al. (1995), Sekiguchi et al. (2006), Van Waerebeek et al. (2010).