Harbor Porpoise (Phocoena phocoena)

The Harbor Porpoise

The Harbor Porpoise (Phocoena phocoena) is the most widely seen porpoise, sometimes earning it the nickname "common porpoise." The Harbor Porpoise belongs to the Cetacean family, a division of water-dwelling mammals that must breathe oxygen. Due to their relatively small size, they have never been actively hunted but often fall prey to fishing nets off of the coast.

Found primarily in the North Atlantic Ocean, the Harbor Porpoise is the only true porpoise in the area. They tend to stay close to the coast and river inlets, sometimes traveling in rivers and venturing miles from open ocean. They are also found in the northern Pacific Ocean, along the coasts of western Canada and the northwest United States.

Harbor Porpoises are somewhat small, only reaching a full adult size of 4-6 feet (1.2-2 meters) and only weighing in at about an average of 140 pounds (63 kg). The females are much heavier than the males, however, and can weigh as much as 167 pounds (76 kg). They are dark gray over most of their bodies, but their sides tend to be lighter gray and their bellies are almost white. They have small, triangle-shaped dorsal fins and a more rounded head without a pronounced beak and have flat teeth.

Porpoises are carnivorous, and their diet consists mainly of fish. They like to hunt schools of fish but will also eat squid, herring, and anchovies. The average porpoise will take in 4% to 9% of their body weight in fish daily. The Harbor Porpoise usually swims without coming completely out of the water, rolling over the waves to catch a breath of air. They can dive in excess of 700 feet to catch fish and use the echoes from their sound waves to locate food and other objects.

Harbor Porpoise reproduction usually occurs once the female has reached at least three years, and the pregnancy lasts about 11 months. The mother porpoise then nurses the calf for at least eight months, and the young porpoise is able to eat some solid food at about three months of age. The prime time for mating is usually between June and September, and a Harbor Porpoise can live about 17 years.

Unlike dolphins, porpoises are very shy animals, traveling alone or in very small groups and not playing in the waves or approaching boats and people. It has also been discovered that a primary threat to the porpoise, aside from accidentally being trapped in fishing nets, is actually the Bottlenose Dolphin. There have been witness reports of pods of dolphins attacking a single porpoise, although the cause of this is not known.

Further Information on the Harbor Porpoise:

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Bibliography:
Harbour Porpoise, Wikipedia, August 4, 2004. http://en.wikipedia.org/wiki/Harbor_porpoise.
Porpoises. Encarta Encyclopedia, © 2000.
The Porpoise Page. The Porpoise Page, © 1998. August 4, 2004. http://www.theporpoisepage.com/harbor.php.