What is the Difference Between a Dolphin and a Porpoise?
27 August 1997
Dolphins and porpoises are so similar that it is easy to confuse which is which.
In general, porpoises are smaller and plumper than dolphins, rarely reaching lengths of more than 6 feet and weights of more than 300 pounds. The dolphin has a rounded head and a small, triangular dorsal fin. Porpoise lack the ‘beak’ characteristic of most dolphins, have a blunt snout.
Most species of dolphins have long streamlined bodies, with a distinct pointed beak and a prominent dorsal fin with a curvature toward the tail. Their size varies from 4 to 26 feet with weights ranging from 70 to 1,500 pounds. Their teeth are sharp and cone-like in shape in contrast to the spade-shaped, laterally compressed teeth of the porpoise.
The bottlenose dolphin is the species of toothed whales most frequently spotted off the North Carolina coast. They are typically inshore species, and most often are observed in groups of about a dozen. Atlantic bottlenose dolphins are robust, though streamlined, growing to lengths of 8 to 11 feet with weights ranging from 500 to 1,000 pounds. They usually have light colored bellies and dark backs, colors that help them blend in with their surroundings. Their lower jaw projects beyond the upper jaw, giving them the appearance of wearing a permanent grin. The bottlenose dolphin is a powerful swimmer and can sometimes be spotted frolicking in the bow wave of a vessel or surfing on large waves.
While some confusion may exist about the differences between porpoises and dolphins, one thing is clear: Their numbers are dwindling due to direct hunting, accidental catches in nets of commercial fishing operations and higher pollution levels in oceans and rivers. The Marine Mammal Protection Act, a federal legislation enacted in 1972, protects porpoises and dolphins and all marine mammals in U.S. waters.