Wildlife Spotlight: Bottlenose Dolphin (Tursiops truncates)
Acrobats Of The Ocean
By Joanne Connery, Development Associate
Published: August 2006
A Bottlenose dolphin leaps. Photo credit: NOAA.
Much is known about this interesting mammal. It is a member of the Cetacean order of animal classification. Other familiar members of this order are whales and porpoises. Of the mammals that live in the sea, the Cetaceans are the most fully adapted to their aquatic lives. They have many physical features that are beneficial to them in their ocean environment. Their body is spindle shaped which allows them to move easily and quickly through the water. Some can swim as fast as 20 mph, but only for brief periods of time. The Bottlenose dolphin’s typical swimming speed ranges from three to six miles per hour. They are strong and agile and can frequently be seen performing acrobatic feats as they leap from the water. Their body coloring ranges from darker grey near their dorsal fin to a much lighter grey on their underbelly. These varied shades of gray are an adaptation that actually provides protection from predators. The darker color on their dorsal or topside makes them blend in with the water when viewed from above. The coloring on their ventral, or underside makes them less visible from below because their light grey, almost white belly makes them less easily seen by predators against the sunlight filtering down from above.
Their size and the percentage of body fat is another excellent adaptation of the Bottlenose dolphin to its environment. The members of this species found in cooler pelagic waters tend to be larger, heavier and have a higher body fat composition than their cousins found in warmer, shallower waters. Their pointy and sharp teeth are located in elongated upper and lower jaws which undoubtedly gave them the bottlenose moniker. These features assist them in capturing prey. When searching for food, this dolphin uses a method called echolocation. They locate their dinner by producing sounds and listening for the echo. An interruption in the echo indicates a possible source of food. As the dolphin moves closer to its prey, the echo becomes louder, enabling them to zero in on the location of the object of interest. Their diet consists mainly of small fish, but they are known to eat octopus, squid and sometimes small crabs. Bottlenose dolphins also have very good eyesight. They have a double-slit pupil which gives them they ability to see well in the air and underwater.
Recently a member of FMSA staff had the opportunity to see these magnificent creatures in their natural habitat. Shannon Lyday, the Volunteer Field Supervisor for the Beach Watch program saw a pod of Bottlenose dolphins up close and personal. Shannon shared the details of her experience, "It was absolutely magical. I was at Baker Beach just before sunrise, as the full moon was setting over Land's End. I saw a movement in the water, and looked over to see half a dozen bottlenose dolphins slowly rolling through the water, only about 10 feet from the shore. I spotted a small dorsal fin among the group, indicating a calf".
Bottlenose dolphins have a broad range. They can be found all over the world in coastal areas and inshore waters and in temperate and tropical seas. They are rarely found above 45° in the Northern hemisphere or below 45° in the Southern hemisphere. The species is abundant and their populations appear to be stable, so they are not considered endangered. However, some particular populations have been declining in number due to water pollution and reduction in food availability.
The Bottlenose dolphin is an interesting and dynamic creature that is home to many ecosystems throughout the world. We are lucky to have them in our National Marine Sanctuaries just offshore. More information can be found on the Bottlenose dolphin and its Cetacean relatives at the websites of our sister sanctuaries: at http://montereybay.noaa.gov, and at http://cordellbank.noaa.gov/.
Photo credit for the acrobatic Bottlenose dolphins: Annie Douglas