Common Bottlenose Dolphin Fact File
The common bottlenose dolphin is among the most recognizable ocean animals due to their popularity in pop culture.
Their body is colored dark grey above with white or cream below.
Their stream-lined body features a dorsal fin on top, a pair of pectoral fins with one on each side of the body and the tail flukes pointing out on either side of the tail.
The head features the short bottle shaped snout from which their name comes.
Behind the head is the blowhole which is used for easy breathing at the surface.
Males are slightly larger than females. On average the males measure 3.8m (12.5ft) long compared to 3.7m (12.1ft) long for females with an average weight of 650kg (1433lbs).
They are the largest of the beaked dolphin species. Animals found in colder regions tend to be larger in size.
Two forms are often recognized the nearshore and offshore. Those individuals considered nearshore are often smaller and lighter in color.
The bottlenose dolphin is a carnivore. Their diet is mostly focused on fish but cephalopods, crustaceans, small rays and sharks are also consumed.
Fish are swallowed head first to ensure the spines do not catch in their throat.
To find food they will emit pulses of sound from their forehead. These may also serve to stun prey and help make them easier to catch.
They can not chew their food. Most is swallowed whole but some is torn in to smaller chunks. Another method to break up food is to shake it in the air and strike it with their tail.
Common bottlenose dolphins have been observed to strand prey and then strand themselves to catch it.
Each day a dolphin will eat as much as 5% of its body weight in food. This may amount to as much as 14.5kg (32lbs) of food.
In areas where dolphins live alongside humans they may follow fisherman’s boats to catch prey or bait which is discarded.
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Common bottlenose dolphins can be found across much of the world’s tropical and temperate oceans. They can be found offshore out to the continental shelf. Some will venture in to bays, lagoons and larger rivers.
These adaptable animals can inhabit a range of habitat such as coastal and pelagic waters along with coastal environments such as estuaries, lagoons and wetlands.
Most populations are resident in one area but some, such as those on the Atlantic coast, will migrate seasonally.
Bottlenose dolphins will mate with multiple partners each breeding season. After mating the male may follow the female to prevent other males from mating with her.
Males will court a female by arching his back, stroking and nuzzling the female and clawing his jaws or yelping.
A single calf is born after a 12 month gestation period. Calves are nursed from nipples on either side of the genital slit. Weaning occurs between 18 and 20 months old.
After weaning they will spend four years with their mother.
The female is responsible for most of the care of the calf. All of the females in the group will help to care for one another’s offspring. From a year old their mother starts teaching them how to hunt.
Females will produce a calf every two to three years. Sexual maturity is reached between five and ten years old for females and eight to thirteen years old for males. Females will continue to reproduce in to their forties.
Common bottlenose dolphins will live in small groups known as pods which range in size from two to three members up to thousands. Sometimes these pods will be mixed with other dolphin species such as the Indo-Pacific bottlenose dolphin.
These may include a range of sub-groups and often these sub-groups will leave and join other groups regularly.
This species is able to hold its breath underwater for up to 4.5 minutes at a time.
They are capable of reaching speeds up to 30kmh (18.6mph).
As social animals they will bond by stroking and rubbing one another. They may show aggression by biting, ramming and tail slapping.
To rest the common bottlenose dolphin will decrease its activity level which allows them to rest one side of their brain while remaining ‘conscious’ and breathing so they can carry out survival tasks.
Common bottlenose dolphins will make a wide range of vocalizations including whistles, grunts, trills, squeaks and moans. Each individual forms their own ‘signature whistle.’
Predators and Threats
Natural predators of the common bottlenose dolphin include large sharks and stingrays may also cause mortality in the species.
They can survive bites from a shark with their blubber helping to provide this protection.
Common bottlenose dolphins face a range of threats from humans. The most high profile of these is their capture for exhibition in zoos, aquariums and marine parks. Further to this they have also been used in military operations.
They are hunted by humans for use as bait, for consumption or to remove a predator of fish stocks which are valuable to people. Often they are caught as bycatch in fishing operations.
Humans may use dolphins to make oils, lubricant, glue and leather goods.
Increasing pollution can lead to mortality in common bottlenose dolphins. Oil spills also affect them. Habitat reduction and degradation is another threat.
Common bottlenose dolphins are one of three bottlenose dolphin species which make up the genus Tursiops. The other two are the Indian Ocean bottlenose or Indo-Pacific dolphin and the Burrunan dolphin.
These animals have a larger brain than humans and show a high degree of intelligence. They have been seen using tools with one population placing sponges over the beaks when they are foraging among sharp coral.
A bottlenose dolphin will have three times more blood in their body than that of a human. This increases their oxygen-storage during dives.
Dolphins shed their outer layer of skin every two hours to increase their efficiency while swimming.
In studies some have shown an ability to recognize themselves a capability seen in few other animals.
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