The Harbor porpoise is a shy and elusive animal typically seen in small pods of 2-5 individuals. While porpoises and dolphins are both members of the toothed whale family, they are distinctly different species. When compared to dolphins, porpoises have a short, rounded face and beak, typically reach approximately 5 feet in length, have a triangular dorsal fin, and spade-shaped teeth. The Harbor porpoise has a charcoal gray coloring on its back with a light gray or white on its sides above the fins with a white underbelly. Females are slightly larger weighing in at 168 lbs and reaching 5’6’’ in length while males weigh 134 lbs and reach a maximum length of 5’2’’. The average life span for both male and female is 24 years.
The Harbor porpoise is a coastal species often found in harbors, bays, and estuaries of northern temperate and subarctic waters. Along the Pacific coast, they can be found from Monterey Bay to the northern Sea of Japan. They can be seen in California waters year-round and researchers consistently spot harbor porpoises swimming underneath the Golden Gate Bridge.
Female harbor porpoises reach maturity between 3-4 years of age and may become pregnant annually for several years in a row. Gestation begins in the late spring or early summer and lasts up to 11 months resulting in most calves born in May-July. Calves are nursed for 8 to 12 months.
Harbor porpoises are known to be solitary and nonsocial, unlike their dolphin cousins. However, little is known about social affiliations and interactions. They usually feed individually on schooling fish such as herring, capelin, sprat, and silver hake and will occasionally eat squid and octopus while traveling many miles per day. Natural predators include large sharks and orcas.
While there are thousands of harbor porpoises, many geographical populations are substantially reduced from historic levels. For example, harbor porpoises were frequently seen in the San Francisco Bay until the 1930s before disappearing for almost 60 years. Due to World War II and the use of submarine nets in the bay to keep enemy boats away, along with an increase in environmental contaminants in the bay from increased industrialization, it is believed the harbor porpoises resided elsewhere. However, in the 1990s, following twenty years of the Clean Air and Water Act, harbor porpoises began reappearing in the Bay. Internationally, the main threats to harbor porpoises are getting caught in commercial fishing gear such as bottom-set gillnets, trawls, and herring weirs and underwater noise pollution that interferes with their communication. See how you can take action around the threats facing harbor porpoises at: Sustainable Seafood.
At The Marine Mammal Center
Today, The Marine Mammal Center’s Cetacean Field Research Program researchers have identified over 600 harbor porpoises in San Francisco Bay that appear healthy and that demonstrate both mating and birthing behaviors. You can contribute to our research by reporting porpoise sightings here. These sightings provide valuable knowledge to our researchers about the health of the species and our shared ecosystem. While rare, the Center has cared for both dolphins and porpoises found stranded along the California coast. Garber, a young male porpoise, was found in Crescent City on the beach suffering from malnutrition and pneumonia. After 3 months of rehabilitation, Garber was released successfully with a satellite tag and tracked between San Francisco Bay, Monterey and even Baja California.