THE ATLANTIC BOTTLENOSE DOLPHIN
Bottlenose dolphins are found worldwide in all warm and temperate waters. In the Atlantic they range from Nova Scotia and Norway to Patagonia and the tip of South Africa. They also range in the Pacific from northern Japan and southern California to Australia and Chile & are common in the Mediterranean Sea and the Indian Ocean.
Adult bottlenose dolphins average 8 to 10 feet in length and weight 300-600 pounds. Males may be slightly larger than females. The average life expectancy is 25 years. Their sleek, torpedo-shaped body is padded by a layer of blubber which helps insulate against heat loss and serves as a fat reserve. Their backside is a dark grey and the sides a lighter gray fading to a whitish color on their underside. This coloration serves as a type of camouflage called counter shading. When viewed from below, the light belly blends into the light shining above. When viewed from above, the darker back blends into the darker colors of the water below.
Dolphins are active predators and opportunistic feeders, eating a wide variety of fish, squid, and crustaceans such as shrimp. They will consume 4 to 6 percent of their body weight in food per day. Dolphins used several feeding strategies: they may hunt individually or cooperatively, herding fish into a tight ball for easy feeding. They also chase fish onto mud banks or herd them into shallower waters where catching prey may be easier.
Bottlenose dolphins are very social animals that live in groups called pods. The size of a pod varies from 2 to 15 animals. Pods may join up temporarily to form larger groups or herds. Up to several hundred animals have been observed traveling in one herd. It’s believed pod composition may be based on age, sex, and reproductive status. Females with their young often make up one group type. At 3 to 6 years of age the juveniles leave their group and form juvenile pods. Young male dolphins join bachelor groups, and juvenile females often return to their maternal group.
Bottlenose dolphins are not an endangered species, but they are protected (along with all marine mammals) in US waters by the Marina Mammal Protection Act of 1972. The worldwide population is unknown due to insufficient data, but certain populations are known to be depleted. Threats include pollution, habitat destruction, accidental catches in fishing gear, and human activities such as boating.
- Interesting Facts:
- Dolphins can swim in bursts of up to 21 miles per hour, are capable of staying submerged for about 8 minutes, can leap as high as 20 feet.
- The deepest trained dive was recorded at 1,795 feet. Dolphins generally dive from depths of 10 to 150 feet.
- Tooth rake marks, evident on dolphins in captivity and in the wild, are a result of scratching each other with their teeth while playing or fighting.
- Dolphins use echolocation to determine the size, shape, density, and texture of an object. It’s like seeing with sound.
- Dolphins have no vocal cords; they produce sounds by moving air around in the nasal passages located around the blowhole.
- Dolphins swallow fish whole and head first. If fish are swallowed tail first, the scales scratch as they go down.
Meet The Zoo’s Dolphins
Semo is darker in color and larger than the other dolphins in the exhibit. He has a relatively short rostrum (beak). Semo is thought to be one of the oldest male dolphins in human care. In his mid-40s, he’s an elderly dolphin no longer able to do the big leaps and fast swims of his prime years. Since his arrival at the Minnesota Zoo in 1991 Semo has sires two calves. A third calf is on its way with Allie. Semo is also thought to be one of the oldest males in human care to sire a calf. Semo has an estimated birth year of 1964.
Spree is the youngest (for now) and smallest of the four dolphins. She is an adolescent dolphin, and is still growing and learning. As her name suggests, she is quite energetic. She is often observed exploring and playing. Much of Spree’s learning is done by watching and then mimicking Semo, and she is learning more and more behaviors every day. One of her favorite behaviors is to emit a bubble ring from her blowhole while at the window. Spree was born at the Minnesota Zoo on August 16, 2002.
April can be spotted by the dark gray coloration on her back along with the dark markings on her head. April is 8 feet long and weighs 430 pounds. She is on loan from the Brookfield Zoo in Chicago, along with her daughter Allie. She is often heard vocalizing during enrichment sessions with her trainers. She successfully mothered three calves: Allie (also at the Minnesota Zoo), Keebler, and Wilson. April has an estimated birth year of 1967.
Allie is distinguished by her long, slender rostrum and light gray coloration, and currently you may notice a baby bump. Allie is pregnant, with a due date in spring 2009. If successful, this will be Allie’s second calf. Her earlier calf was named Balla. She arrived at the Minnesota Zoo on January 14, 2008, along with her mother April. She is also on loan from the Brookfield Zoo in Chicago. Aliie was born on April 1, 1987 and is in the prime of her dolphin life.
Information courtesy of www.mnzoo.org