There are two physically different kinds of common dolphins. Some have long rostrums, or beaks, while some have short. Scientists looked into these two different types of dolphins to see if they could be considered two different species. A number of aspects were researched: the length of the rostrum, the number of teeth, coloration, and DNA. Besides the difference in sizes, the coloration in a long-beaked common dolphin is a bit more muted than that of a short beaked dolphin. Their results lead them to conclude that yes, common dolphins are either long beaked, or short beaked. Long beaked common dolphins now have the genus species Delphinus capensis while short beaked common dolphins are known by the genus species Delphinus delphis. Both long and short beaked common dolphins can be found in all oceans, even travelling together in the same pods. A long beaked common dolphin can have as many as 200 teeth! These sharply pointed teeth are ideal for grasping slippery fish and squid.
Common dolphins are very social animals, and travel together in large groups, or pods. Sometimes these pods can number to over 1,000 individuals. These dolphins can often be seen doing many different behaviors, such as leaps through the water as they swim rapidly. Sometimes they'll breach, coming out of the water and landing on their back or side. Or maybe, they may ride at the front of a ship, letting the pressure created by the ship carry them through the water without much effort, as the dolphin in the picture below is doing. Several individuals may ride at the same time, darting back and forth quickly. When they get tired of riding along with the boat, or when they feel like going in a different direction, they'll just travel off on their own. It seems that sometimes they bowride just for the sheer fun of it. This dolphin on the right has a white spot near the top of its head, as it quickly breaks the surface of the water to get a breath. Watching a dolphin bow ride can be an incredible experience.
Common dolphins can reach a length of 2.5 m, though most tend to be slightly smaller than that, with males being a bit larger than females. At birth, these dolphins are around 80 cm in length. They are born after a gestation period of about 10 to 11 months.
These dolphins are typically found in warmer waters, though individuals may be sighted as far north as Canada. Sometimes they can be found farther north in the spring, when waters are a bit warmer. Their range extends well above and below the equator line, and they can be found quite a ways offshore.
Common dolphins are not rare, though they do experience a significant mortality rate due to fishing. Common dolphins are sometimes found with yellowfin tuna. When the tuna is caught up in a purse seine net, dolphins can also be caught, and many of them die either by getting tangled in the net and drowning, or when brought on deck. The Marine Mammal Protection Act in 1972 helped to reduce the number of dolphins killed, but many individuals of several species are still being slaughtered.
last updated 7/15/00
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