Ask the Aquarium - Is it a dolphin or a porpoise?
Q We thought we were seeing porpoises swimming off Ocean Isle Beach, but someone said they were dolphins. Are dolphins and porpoises the same thing?
A. People often use the terms dolphin and porpoise interchangeably. Although these marine mammals look much alike, they are different animals. Dolphins (family Delphinidae) have a rostrum, or beak, and a curved dorsal fin. Porpoises (family Phocoenidae) have a blunt head and a triangular dorsal fin.
In North Carolina waters, it is common to see groups of dolphins feeding close to shore. Porpoises tend to inhabit offshore waters in colder climates. The nearest porpoise species, the harbor porpoise, ranges between Canada and Virginia; however, in winter they're known to enter North Carolina waters as far south as Cape Hatteras.
Porpoises are considered relatively nonsocial animals, usually seen in groups of two to five. Dolphins, on the other hand, travel in larger groups and display frolicking, acrobatic behaviors.
In nearshore North Carolina waters, you're most likely to see bottlenose dolphins. Other species, such as spotted dolphins, travel our offshore waters.
Like all marine mammals, porpoises and dolphins are protected by the Marine Mammal Protection Act. It's against federal law to approach, feed, or harass them, and violations are punishable by fines or imprisonment.
Both dolphin and porpoise populations continue to be threatened by human activities. Unintentional entanglement in commercial and recreational fishing gear, ingestion of litter, contamination of food sources and boat injuries remain problems.
As wild marine mammals, these animals are best appreciated from a distance. People often make the mistake of using food to entice them close to boats. This has resulted in some animals becoming accustomed to approaching boats for handouts. Not only is this bad for the animal's diet, it can endanger both the animal and people. Dolphin wounds from boat propellers are not uncommon, and animals have been known to become aggressive and bite.
Litter and cruel jokes are also a problem. Lens caps, fishing hooks, lures, disposable lighters and other such items have been found inside dead dolphin stomachs.