November 24, 2009
Animal Snapshot: Harbor Porpoises
Little whale, big problem
Just the Facts:
Are they really whales? Harbor porpoises are cetaceans, which means they are related to dolphins and whales.
How big are they? Among the smallest of marine mammals, harbor porpoises are about 26 inches long when born and reach around 5 feet.
How long do they live? Around 15 years.
Do they grow up quickly? A young harbor porpoise—only one is born at a time—stays with his or her mother for approximately 6-10 months, first nursing and then learning from her how to catch prey.
What about eating? They have 19-26 small spade-shaped teeth with which they grab their prey and swallow whole. Small schooling fish such as mackerel, herring and capelin make up their diet.
How do they know where they are in the ocean? Like dolphins, they make a chain of clicks that produce echoes as they bounce off objects in the water. This echolocation helps them navigate in murky waters and find food.
Are they social? Harbor porpoises aren’t like dolphins or orcas: They are generally found alone or in transient groups of 2 to 5, though occasionally larger groups are spotted. As far as interacting with humans goes, these porpoises are shy and not easy to approach; they definitely don’t swim near boats or bow ride, the way dolphins do.
Where can I see them? You’ll find harbor porpoises in the colder, northern waters of the Atlantic and Pacific. If you live in the United States, you could find them from Alaska through Oregon in the Pacific and From Canada through North Carolina in the Atlantic, depending on the season.
Danger in the Water
The greatest threat to harbor porpoises is fishing. As their name implies, harbor porpoise are often found close to shore. In coastal waters, they may run into fishing nets as they pursue small fish, either in the frenzy of the chase or when swimming quietly and not using their echolocation.
When the porpoises thrash in attempt to free themselves, they become hopelessly entangled and drown. We don’t know exactly how many die worldwide each year, but we do know that thousands die each year worldwide and that entanglement in fishing gear is a leading threat to the species’ survival.
The Humane Society of the United States has been a long history of fighting to protect harbor porpoises from death in fishing nets. Learn more about our efforts.