The Introvert and the Extrovert

by Gail Wellenstein, Kitsap Beach Naturalist

Traffic inched its way westward on the floating bridge, providing the perfect opportunity to check what was hanging out in the Hood. Surf scoters and pigeon guillemots gently bobbed on the calm water while seagulls soared overhead. Out of the corner of my eye, I picked up a different motion, easily missed, of two sleek gray backs with a small triangular dorsal fin arching slightly above the water and silently disappearing. As we crept forward, they seemed to follow us, the Harbor porpoises smoothly repeating this shallow curve as they hunted for schooling fish in the eddies created by the bridge.

Harbor Porpoise model at Port Townsend Marine Science Center. Photo Credit: Gail Wellenstein

Whales, dolphins and porpoises are members of the order called Cetaceans. They are all carnivorous mammals that have blowholes, horizontal tail flukes and streamlined bodies. We call them whales if they are twenty feet or longer. Dolphins are toothed whales under twenty feet with beak like snouts, hooked dorsal fins, and cone shaped teeth like an orca. Porpoises are the smallest of the cetaceans with small, rounded heads without a beak, a triangular dorsal fin, and spade-shaped teeth like a beluga. Here in the Salish Sea, we have two species, the introverted Harbor porpoise who quietly travels alone or in a pair and the extroverted Dall's porpoise with their flashy, noisy, frolicking attitude. They are the bow riders sending up rooster tails while you may see a harbor porpoise quietly following in the wake of your boat.

Harbor porpoises are dark gray and are the size of an average woman, around 5 ½ feet and between 135-170 pounds. They hunt for schooling fish like herring, pollock, and sand lances, with the occasional squid or octopus. Their average lifespan is ten years, but they can live up to twenty-four. They are a dominant predator in our area but sometimes fall prey to Biggs killer whales. Females reproduce starting at age four and have an eleven-month pregnancy. As their name suggests, they are found along coastlines, bays, and estuaries, and do not migrate.

Dall's porpoises are larger, like an NBA player, up to 7 feet and 350 pounds and look a bit like a miniature orca. They are mostly black with white patches on their flanks and trailing edge of their dorsal fin. Fitting in with their more extroverted nature, you will find them in larger groups. Their diet, lifespan and reproduction patterns are similar to the harbor porpoise. They are fond of cold water and are more of an offshore species than the harbor porpoise.

In the 1940s, the harbor porpoise was the most common cetacean in Puget Sound. By the 1970s they had disappeared completely from Puget Sound and only a few remained around the San Juans and the Straits. This population crash was due to a number of factors. After World War II, gillnetting became a common fishing method throughout the Salish Sea, and the harbor porpoise was getting caught up in the nets. The lumber industry and the rapid increase in other industries in the area also led to significant water pollution; toxins are stored in blubber and affect the immune system, hormone levels, and reproduction. The population began to rebound in the early 2000's, due to a combination of improved fishing practices to reduce the bycatch as well as a concerted effort to clean up the Sound and we now have over 11,000 in the Salish Sea.

Dall's porpoises also are vulnerable to fisheries bycatch, leading to a moratorium on commercial driftnets in the North Pacific. Their population has been relatively stable since the moratorium but the population in the Salish Sea has declined since the 1990s, to the point that they are now a rare sight here. Scientists speculate that this decline is associated with the strong rebound of the harbor porpoise population. They hunt the same food and perhaps the Dall's porpoise just has decided to leave town for easier pickings on the coast, leaving the Salish Sea for those quiet homebody cousins.