Striped dolphin

Habitat: Oceanic species of warm and temperate waters, mainly well beyond continental shelf of depths > 1000 m.

Description: Slender, torpedo-shaped body, elongated beak with 39 - 50 pairs of sharp, slightly incurved teeth in each jaw. Distinct groove separates beak from forehead. Colouration variable; dark grey or bluish grey on back, lighter grey flanks, white belly. Two distinctive stripes on flanks; one from eye to anus, often doubled by secondary thinner and lighter stripe originating from this band and turning downwards towards flippers; one thick black stripe from below eye to flippers. Conspicuous light grey blaze originates above and behind eye, narrowing to a point below dorsal fin; posterior part of flanks light grey, sometimes upwards over dorsal surface of tail stock - gives appearance of black 'brush mark' originating behind dorsal fin and running forwards over light grey flank. Flippers are tapering, black, inserted in white region, although some individuals' flippers are pale towards base. Dorsal fin is slender, sickle-shaped, black. Tail stock narrow with no obvious keel, flukes are dark with median notch.

Size: Female 1.85 m on average, maximum 2.25 m; male 2.0 m on average, maximum 2.4 m.

Weight: 70 - 90 kg, maximum 130 kg.

Lifespan: Probably 30 - 35 years, maybe up to 58 years.

Distribution: Worldwide, mainly tropical and warm temperate waters. In NE Atlantic, occurs mainly offshore from the continental shelf of Spain, Portugal, France. Occasional visitor around British Isles, recorded mainly from SW; occasionally further north to Scotland. 5 strandings per year on British and Irish coasts 1913 - 1969 (average 0.09 / year); 9 strandings 1970 - 1984 (average 0.60 / year); 145 strandings 1985 - 1999 (9.67 / year). Sharp increase could indicate that species is ranging further north, possibly reflecting warmer sea temperatures.

Diet and feeding: Variety of meso- and bentho- pelagic fish, and crustaceans. Diet probably various regionally.

Breeding: Reproductive parameters vary with exploitation pressure and populations. Gestation period around 12 months; lactation period between 8 - 20, usually 12 - 14, months; calving interval 2 - 4 years. Average age at sexual maturity varies between populations; in Mediterranean, males 12 years, females 14 years; E North Atlantic, males 7 - 14 years, females 15 - 18 years. Breeding season extended, probably variable; July - October in Mediterranean, April - May N E Atlantic.

Conservation status and population: Listed by IUCN as lower risk, conservation dependent. Only population estimate for NE Atlantic covered continental shelf off SW Ireland and NW France, excluding Bay of Biscay, NW Spain - 73,843.

Occasionally hunted in S Europe. Substantial bycatch in French tuna drift net fishery; annual catch around 1200, representing around 1.6% of estimated population in area. Estimated 12,635 striped dolphins killed by French, Irish, and British drift net fisheries 1990 - 2000. Recent ban on drift nets and change to pelagic trawls has led to decline in number of bycaught striped dolphins.

High pollutant levels found in blubber from French and Mediterranean regions.

Never maintained successfully in captivity.

Identification

Small, swift dolphin, slender beak; superficially resembles common dolphin but beak is shorter. Always in groups. Frequently breaches clear of water, showing black lateral stripes from eye to flipper and eye to anus. Lacks yellow patches of common dolphin.

Vocalisations: Emits clicks 0.3 - > 100 kHz at repetition rates of up to 900 clicks /s. FM whistles 3.5 - 28.5 kHz, mainly around 10 kHz.