Bottlenose Dolphins (Tursiops truncatus)
The Bottlenose Dolphin is the most common and well-known dolphin species. It inhabits warm and temperate seas worldwide and may be found in all but the Arctic and the Antarctic Oceans. Bottlenose Dolphins prefer shallow, inshore waters and are commonly seen off the coasts of Hawaii and Florida.
Relatives of the Bottlenose Dolphin include the Pacific White-sided Dolphin (Lagenorhynchus Obliquidens), distinguished by its tapering head, grey-white belly and tall dorsal fin, The Risso's Dolphin (Grampus Griseus), which is identified by its large size and blunt, beakless head and the White-beaked Dolphin (Lagenorhynchus Alborostris), a large acrobatic swimmer with a stubby tail.
Bottlenose Dolphin Characteristics
Bottlenose Dolphins have streamlined, torpedo-shaped bodies that enables them to glide swiftly through the ocean. Bottlenose Dolphins range in colour from cream to charcoal or almost black. Usually, their backs are darker and their bellies are lighter. The elongated upper and lower jaws give the animals their name of Bottlenose.
The real nose however is the blowhole on top of the head, and the nasal septum is visible when the blowhole is open. Their face shows a characteristic 'smile'. Bottlenose Dolphins grow 2 - 4 metres (6 - 13 feet) in length and weigh around 500 kilograms (1,100 pounds). Male Bottlenose Dolphins are slightly longer and considerably heavier than females on average.
Bottlenose Dolphins have distinctive skin markings that help them camouflage from potential predators. Their tails have two horizontal paddles, called 'flukes' which contain no bones or muscles, these help power them through the water.
Bottlenose Dolphin Behaviour
This highly intelligent aquatic mammal has always been depicted as one of mans best ocean friends. The largest of the beaked dolphins, it is named for its short, stubby beak which resembles the top or neck of a bottle.
Bottlenose Dolphins live in social groups called 'Schools' or 'Pods' containing up to 12 individuals These are long-term social units. Typically, a group of females and their young live together in a pod, and juveniles in a mixed pod. Several of these pods can join together to form larger groups of one hundred dolphins or more. Males live mostly alone or in groups of 2 - 3 and join the pods for short periods of time.
The Bottlenose Dolphin is commonly known for its friendly character and curiosity towards humans immersed in or near water. It is not uncommon for a diver to be investigated by a group of them and they are often quite receptive to being gently patted or stroked. Occasionally, dolphins have rescued injured divers by raising them to the surface, a behaviour they also show towards injured members of their own species.
Bottlenose Dolphins are predators however, and they also show aggressive behaviours. This includes fights among males for rank and access to females, as well as aggression towards sharks and other smaller species of dolphins. Male dolphins, during the mating season, compete very vigorously with each other through showing toughness and size with a series of acts such as head butting.
Often seen riding the bow wave of a boat and 'breaching' (doing belly-flops), the Bottlenose Dolphin can leap several metres out of the water. They perform these high leaps and somersaults to breathe and also to communicate with each other.
Bottlenose Dolphins sleep about eight hours a day, swim speeds of 12 miles per hour and dive for up to 20 minutes at depths of 300 metres (1,000 feet).
Bottlenose Dolphin Diet
Their diet consists mainly of small fish, occasionally also squid, crabs, octopus, and other similar animals. Bottlenose Dolphins feed on around 8 - 15 kilograms of food per day.
Bottlenose Dolphins have 18 - 27 pairs of small conical teeth in both jaws. Their peg-like teeth serve to grasp but not to chew food.
When a shoal of fish has been found, the animals work as a team to keep the fish close together and maximize the harvest. Bottlenose Dolphins also search for fish alone, often bottom dwelling species. Sometimes they will employ 'fish whacking' whereby a fish is stunned (and sometimes thrown out of the water) with the fluke to make catching and eating the fish easier.
Bottlenose Dolphin Senses and Communication
Bottlenose Dolphins communicate with each other using body language and distinctive whistles, clicks and sounds produced by six air sacs near their blow hole (they lack vocal cords). Each animal has a characteristic frequency-modulated narrow-band signature vocalization (signature whistle) which is uniquely identifying. Other communications use about 30 other distinguishable sounds.
Bottlenose Dolphin Reproduction
The main breeding season for the bottlenose dolphin is between March and April.
Courtship - Courtship behaviour of the male includes clinging along to the female, posing for the female, stroking, rubbing, nuzzling, mouthing, jaw clapping, and yelping. Copulation is preceded by lengthy foreplay; then the two animals arrange themselves belly to belly, the penis extends out of its slit and is inserted into the vagina. The act lasts only 10 - 30 seconds, but is repeated numerous times, with several minutes break in between.
Gestation and Birth - The gestation period of the female Bottlenose Dolphin is 12 months. Calves are born in midsummer in European waters and between February and May in Florida. The young are born in shallow water, sometimes assisted by a 'midwife' (which may be male). The new single calf measures about 1 metre (3 feet) long at birth.
To speed up the nursing process, the mother can eject milk from her mammary glands. There are two slits, one on either side of the genital slit, each housing one nipple. The calf is nursed for 12 to 18 months.
The young live closely with their mother for up to 6 years. The males are not involved in the raising of their offspring. The females become sexually mature at age 5 - 12 years, the males a bit later, at the age of 10 - 12 years.
Bottlenose Dolphin Natural Predators
Large shark species such as the tiger shark, the dusky shark, and the bull shark prey on the Bottlenose Dolphin. However, the dolphin is far from helpless against its predators and it has been known to fight back by charging at its attacker. The Orca may also prey on it, but this seems very, very rare.
Bottlenose Dolphin Conservation
Although still generally plentiful, Bottlenose Dolphins have been virtually wiped out in some places. They are hunted for meat and other products in parts of the world
In the Pacific, they are often drowned in tuna nets, although new 'dolphin-friendly' nets are now being used more widely. There have also been concerns about man-made marine noises such as shipping sonar. These noises upset whales and dolphins and affect their ability to feed, navigate and communicate. Evidence suggests that military submarine detection systems producing Low Frequency Active Sonar, floods the oceans with noise and threatens the survival of whales and dolphins by destroying their hearing and causing their ears and lungs to haemorrhage.
Dolphins and Humans
Bottlenose Dolphins (as well as other dolphins) are often trained to perform in dolphin shows. Some animal welfare activists claim that the dolphins there are not adequately challenged and that the pools are too small; others maintain that the dolphins are well cared for and enjoy living and working with humans.
Eight Bottlenose Dolphins that were washed out of their aquarium pool during the devastating August 2005 strike of Hurricane Katrina were later found alive by rescue forces, huddled together in coastal waters near their former home in Gulfport, Mississippi, USA.
Direct interaction with dolphins is used in the therapy of severely handicapped children.
Bottlenose Dolphin |
Atlantic Spotted Dolphin |
Pantropical Spotted Dolphin |
Striped Dolphin |
Rough-toothed Dolphin |
Commerson's Dolphin |
Hector's Dolphin |
Common Dolphin |
Risso's Dolphin |