Atlantic white-sided dolphins and white-beaked dolphins are approachable and curious, although some books have claimed that the white-beaked dolphin is shy. From time to time, both species will ride the bows of boats. Like dolphins in many parts of the world, the Gulf of St Lawrence dolphins often stay close to the larger whales and at times socialize with and even bother them. Using close-up camera work, Sears has documented the presence of tooth marks and scars on the fins of the whales that could have been made only by dolphins. It is difficult to say why dolphins would bite a whale, but maybe they regard it as a potential member of the school and are just testing or evaluating it.
Atlantic white-sided and white-beaked dolphins are closely related, belonging to the same genus, Lagenorhynchus. In the outports of Newfoundland, fishermen call the white-beaked "squidhound" and the Atlantic white-sided "jumper." In fact, both eat squid as well as fish, and both are good jumpers. They live in the cooler temperate waters of the North Atlantic, and their ranges overlap. Yet a student of wild whales will note certain differences. The white-beaked dolphin seems to prefer more northerly waters and can be seen swimming at the edge of the polar ice.
How do Sears and his team distinguish teh two species when dolphins sometimes swim together in herds of 500 to 1,000 or more? The animal's white beak is usually difficult to see underwater. To make matters more confusing, some white-beaked dolphins have black beaks, just like Atlantic white-sided dolphins. Researchers have found that the best clue for identifying the white-beaked dolphin is the white patch on its side, just below the dorsal fin, that continues back and up onto the saddle, the area directly behind the dorsal fin. By contrast, the Atlantic white-sided dolphin has a white patch on the side below the dorsal fin that goes straight back and turns into bright yellow or tan. Even on a cloudy day, with the dolphins skimming through the sea, the yellow patch seems to glow.
Lagenorhynchus acutus
Size: 2.3 to 2.5 m, 165 kg. Males slightly larger than females
Calves at birth: 110 cm
Teeth: 29 to 40 small, sharp-pointed teeth on each side of upper
and lower jaws
Food: Fish (herring, cod, mackerel, hake and others), squid and
crustaceans
Habitat: Mainly offshore waters
Range: Temperate and subpolar waters of North Atlantic
Status: Population unknown, but probably tens of thousands to low
hundreds of thousands