Saturday, December 19, 2009

White-Sided Dolphin and Porpoise

Pacific White-sided Dolphin
The Pacific white-sided dolphin is common in offshore waters along the Pacific Northwest. They have a distinctive pattern of white, gray and black. The two most distinguishing features are the rather blunt beak and the rear-pointing dorsal fin, which is dark on the leading edge and pale gray on the trailing edge. They do not make a distinct blow, but often splash about producing sprays that resemble a blow. They are commonly seen in groups of 10-50 leaping acrobatically, surfing ocean waves, bow riding and “porpoising” in unison. Pacific white-sided dolphins feed on a variety of small fishes and squid, consuming about 20 pounds of food per day. Calving and mating occur from late spring to fall with gestation estimated at nine to 12 months. Adults are about seven feet long and weigh about 200 pounds.

Harbor Porpoise
The Harbor porpoise is very common in coastal waters of less than 600 feet. They are very shy, seldom showing much of themselves above water and almost never performing acrobatics like the dolphins. The best way to identify them is by their small gray body, shy behavior and the rather distinctive sound they make when they breathe. When a harbor porpoise breaks the surface, it makes a quick sneezing sound. They usually live in small groups of two to five individuals. Harbor porpoises feed in mid-water or near the bottom on small fish such as anchovies and herring. Mating usually occurs in early summer with gestation taking 11 months. Adults are about five feet long and weigh about 130 pounds.