The Atlantic White-Sided Dolphin
Lagenorhynchus acutus
The white-sided dolphin are black or dark purple to grey, with a yellowish
blaze along each side to the tail behind the dorsal fin, and a white band
on the flank below the dorsal fin. Below the dark dorsal is a pale grey stripe
along the length of the body. The belly is a pale, yellowish cream and there
are large black genital blazes. There are a dark stripe between the corner
of the jaw and the anterior insertion of the flippers, which joins the large
dark eye patch. They have between 29 and 40 teeth. Female white-sided dolphins
can reach 2.4m and males 2.7m in length and weigh from between 182 and 234kg.
Where can i found them:The Atlantic white-sided dolphin can
only be found in the cool waters of the North Atlantic Ocean and is often
found along the continental . They range from West Greenland up to the northern
United States in the west, and from Iceland, east Greenland, western Norway
and the British Isles in the east. White-sided dolphins have been seen in
small groups, but commonly form larger pods of up to 1,000 animals.
What do they eat:
White-sided dolphins feed on small schooling fish and squid. In the western
North Atlantic short-finned squid, herring, smelt, and shrimp have also been
found in the stomach.
How long do they live
Female white-side dolphins is pregnant for about 11 months. The lactation
period lasts about 18 months, and they calve every 2.5 years. White-sided
dolphins are live for at least 27 years. Sharks and killer whales hunt white-sided
dolphins, and mass strandings are common.
Conservation concerns
Atlantic white-sided dolphins are hunted in the Faeroe Islands and Greenland.
In the past, more than 500 have been killed in one year in the Faeroes. The
catch in southwest Greenland is smaller, probably less than 50 dolphins.The
dolphins are also killed caught in fishing nets throughout their range. Monofilament
gill nets are the biggest threat in the coastal shelf waters of the US, Canada
and western Europe.
Length
1.08-1.12m/3.6-3.7ft (newborn); 2.0-2.8m/6.6-9.2ft (adult).
Head & Beak
Sloping head with short, thick black beak.
Markings
Large, often erect, strongly sickle-shaped dorsal fin, centrally-placed. Black
on back, elongated yellow-ochre band extending backwards from upper edge of
a long white oval blaze.
ID
Less agile than common & striped dolphins, but active at surface, commonly
breach, occasionally bow-ride; tall curved fin; body black with long white
then ochre blaze; no white on back behind fin.
Distribution
Common offshore in deep Atlantic waters west of Norway, around Iceland and
the Faroe Islands, Northern Isles and west of the Outer Hebrides, North Scotland.
Also in northern North Sea, but rare south of here and in the Channel. Recorded
all months of the year but in UK coastal waters, large numbers occur particularly
July to September.
These colorful animal have a white stripe running down their gray side, with a yellowish-tan patch near the tail. They are highly social, gathering in pods of several individuals to several hundred. They are social animals, and are sometimes found traveling with other species, such as fin whales and pilot whales. They are also fairly social around boats, often "surfing" in the wave created by the boat as it cruises along. This wave helps them swim more efficiently.
Wellfleet Harbor can be a dangerous place for marine mammals. Its 15-foot tidal swings and oozy bottom make a trap for any large animal careless enough to linger in its estuaries as the tide begins to fall. In this case, all the conditions were right and the tidal timing was perfect.
References:
Atlantic White-sided Dolphin by Frank Cipriano, Encyclopedia of Marine Mammals pp49-51.
National Audubon Society: Guide to Marine Mammals of the World.
Encyclopedia of Marine Mammals.