   #copyright

Bottlenose Dolphin

2007 Schools Wikipedia Selection. Related subjects: Mammals

                             iBottlenose Dolphin
   A Bottlenose Dolphin at SeaWorld San Antonio in San Antonio, Texas, USA
   A Bottlenose Dolphin at SeaWorld San Antonio in San Antonio, Texas, USA
   Size comparison against an average human
   Size comparison against an average human

                             Conservation status

   Data deficient (DD)
                          Scientific classification

   Kingdom: Animalia
   Phylum:  Chordata
   Class:   Mammalia
   Order:   Cetacea
   Family:  Delphinidae
   Genus:   Tursiops
   Species: T. truncatus

                                Binomial name

   Tursiops truncatus
   Montagu, 1821
   Bottlenose Dolphin range (in blue)
   Bottlenose Dolphin range (in blue)

   The Bottlenose Dolphin (Tursiops truncatus) 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.

Physical description

   Bottlenose Dolphins are grey, varying from dark grey at the top near
   the dorsal fin to very light grey and almost white at the underside.
   This makes them harder to see both from above and below when swimming.
   The elongated upper and lower jaws form what is called the rostrum and
   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".

   Adults range in length from 2 to 4  metres (6 to 13  ft) and in weight
   from 150 to 650  kilograms (330 to 1430  lb), however in most parts of
   the world the adult's length is about 2.5 m (8 ft) and adult weight
   ranges form 200 to 300 kg (440 to 600 lb), with males being slightly
   longer and considerably heavier than females on average. The size of
   the dolphin appears to vary considerably with habitat. Most research in
   this area has been restricted to the North Atlantic Ocean, where
   researchers have identified two ecotypes. Those dolphins in warmer,
   shallower waters tend to have a smaller body than their cousins in
   cooler pelagic waters. For example a survey of animals in the Moray
   Firth in Scotland, the world's northernmost resident population,
   recorded an average adult length of just under 4 m (13 ft). This
   compares with a 2.5 m (8 ft) average in a population off Florida. Those
   in colder waters also have a fattier composition and blood more suited
   to deep-diving.

   The flukes (lobes of the tail) and dorsal fin are formed of dense
   connective tissue and don't contain bones or muscle. The animal propels
   forward by moving the flukes up and down. The pectoral flippers (at the
   sides of the body) serve for steering; they contain bones clearly
   homologous to the forelimbs of land mammals (from which dolphins and
   all other cetaceans evolved some 50 million years ago). In fact,
   recently, in Japan, a Bottlenose Dolphin was discovered to have two
   additional pectoral fins, or "hind legs", at the tail, appearing to be
   about the size of a human's pair of hands. Scientists believe that a
   mutation must have caused the ancient trait to reassert itself.

Taxonomy

   Scientists have long been aware that the Bottlenose Dolphin might
   consist of more than one species. The advent of molecular genetics has
   allowed much greater insight into this previously intractable problem.
   The consensus amongst scientists is that there are two species:
     * the Common Bottlenose Dolphin (T. truncatus), found in most warm to
       tropical oceans; colour sometimes almost blue; has a dark line from
       beak to blowhole
     * the Indo-Pacific Bottlenose Dolphin (T. aduncus), living in the
       waters around India, Australia and South-China; back is dark-gray
       and belly is white with gray spots.

   The following are sometimes recognized as subspecies of T. truncatus:
     * the Pacific Bottlenose Dolphin (T. gillii or T. truncatus gillii),
       living in the Pacific; has a black line from the eye to the
       forehead
     * the Black Sea Bottlenose Dolphin (T. truncatus ponticus), living in
       the Black Sea.

   Much of the old scientific data in the field combine data about the two
   species into a single group - making it effectively useless in
   determining the structural differences between the two species. Indeed,
   the IUCN lists both species as data deficient in their Red List of
   endangered species precisely because of this issue.

   Some recent genetic evidence suggests that the Indo-Pacific Bottlenose
   belongs in the genus Stenella, it being more like the Atlantic Spotted
   Dolphin (Stenella frontalis) than the Common Bottlenose. The taxonomic
   situation of these animals is likely to remain in flux for some time to
   come.

Behaviour and life

   A wild Bottlenose Dolphin playing in the wake of a boat in Florida.
   Enlarge
   A wild Bottlenose Dolphin playing in the wake of a boat in Florida.

   Bottlenose Dolphins typically swim at a speed of 5-11 kilometres per
   hour (3-6 mph); for short times, they can reach peak speeds of
   35 kilometres per hour (21 mph).

   Every 5-8 minutes, the dolphins have to rise to the surface to breathe
   through their blowhole. (However, on average, they breathe more often -
   several times per minute.) Their sleep is thus very light; some
   scientists have suggested that the two halves of their brains take
   turns in sleeping and waking. It has also been suggested that they have
   tiny periods of ' microsleep'.

   Bottlenose Dolphins normally live in groups called pods, containing up
   to 12 animals. 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 species 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. Occasionally, dolphins
   have rescued injured divers by raising them to the surface, a behaviour
   they also show towards injured members of their own species. Such
   accounts have earned them the nickname of "Man's best friend of the
   sea". In November 2004, a more dramatic report of dolphin intervention
   came from New Zealand. Three lifeguards, swimming 100 m (328 ft) off
   the coast near Whangarei, were reportedly approached by a 3 m (10 ft)
   Great White Shark. A group of Bottlenose Dolphins, apparently sensing
   danger to the swimmers, herded them together and tightly surrounded
   them for forty minutes, preventing an attack from the shark, as they
   returned to shore.

   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, orcas, 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.

   Female Bottlenose Dolphins live for about 40 years; the more stressful
   life of the males apparently takes its toll, and they rarely live more
   than 30 years.

Diet

   Their diet consists mainly of small fish, occasionally also squid,
   crabs, octopus, and other similar animals. 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. They 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.

Senses and communication

   The dolphin's search for food is aided by a form of echolocation
   similar to sonar: they locate objects by producing sounds and listening
   for the echo. The broadband burst pulse clicking sounds are emitted in
   a focused beam towards the front of the animal. They have two small ear
   openings behind the eyes, but most sound waves are transmitted to the
   inner ear through the lower jaw. As the object of interest is
   approached, the echo grows louder; the dolphins adjust by decreasing
   the intensity of the emitted sounds. (This is in contrast to the
   technique used by bat echolocation and human sonar where the
   sensitivity of the sound receptor is attenuated.) As the animal
   approaches the target, the interclick interval also decreases, as each
   click is usually produced after the round-trip travel time of the
   previous click. Details of the dolphin's echolocation, such as signal
   strength, spectral qualities, discrimination abilities, etc., have been
   well investigated by researchers. Also, Pack & Herman demonstrated that
   Bottlenose Dolphins are able to extract shape information from their
   echolocative sense, suggesting that they are able to form an "echoic
   image" of their targets.

   They also have sharp eyesight. The eyes are located at the sides of the
   head and have a tapetum lucidum which aids in dim light. Their
   horseshoe-shaped double-slit pupil enables the dolphin to have good
   vision in both in-air and underwater viewing, despite the differences
   in density of these media. Underwater, the eyeball's lens serves to
   focus light, whereas in the in-air environment, the typically bright
   light serves to contract the specialized pupil, resulting in sharpness
   from a small-aperture (similar to a pinhole camera).

   By contrast, their sense of smell is very poor, as would be expected as
   the blowhole, the analogue to the nose, is closed in the underwater
   environment, and opens only voluntarily for breathing. The olfactory
   nerves as well as the olfactory lobe in the brain are missing. The
   sense of taste has not been well-studied, although dolphins have been
   demonstrated to be able to detect salty, sweet, bitter (quinine
   sulphate), and sour (citric acid) tastes. Anecdotally, some animals in
   captivity have been noted to have preferences for food fish types
   although it is not clear that this preference is mediated by taste.

   Bottlenose Dolphins communicate with one another through squeaks,
   whistles, and body language. Examples of body language include leaping
   out of the water, snapping jaws, slapping tails on the surface of the
   water, and butting heads with one another. All of these gestures are a
   way for the dolphins to convey messages.

   The sounds and gestures that Bottlenose Dolphins produce help keep
   track of other dolphins in the group and alert other dolphins to
   possible dangers and nearby food. Bottlenose Dolphins produce sounds
   using 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
   communication uses about 30 distinguishable sounds, and although
   famously proposed by John Lilly in the 1950s, a "dolphin language" has
   not been found. However, Herman, Richards, & Wolz demonstrated the
   comprehension of an artificial language by two Bottlenose Dolphins
   (named Akeakamai and Phoenix) in the period of scepticism toward animal
   language following Herbert Terrace's critique.

Intelligence

Cognition

   Cognitive abilities investigated in the dolphin include concept
   formation, sensory skills, and the use of mental representation of
   dolphins. Such research has been ongoing from the late 1970s through to
   the present, and include the specific areas of: acoustic mimicry,
   behavioural mimicry (inter- and intra-specific), comprehension of novel
   sequences in an artificial language (including non finite state
   grammars as well as novel anomalous sequences), memory, monitoring of
   self behaviours (including reporting on these, as well as avoiding or
   repeating them), reporting on the presence and absence of objects,
   object categorization, discrimination and matching (identity matching
   to sample, delayed matching to sample, arbitrary matching to sample,
   matching across echolocation and vision, reporting that no identity
   match exists, etc.), synchronous creative behaviours between two
   animals, comprehension of symbols for various body parts, comprehension
   of the pointing gesture and gaze (as made by dolphins or humans),
   problem solving, echolocative eavesdropping, attention, mirror
   self-recognition, and more. Recent research has shown that dolphins are
   capable of comprehending numerical values. In an experiment where a
   dolphin was shown two panels with a various number of dots of different
   size and position, the dolphin was able to touch the panel with a
   greater number of dots, much more rapidly than many human beings could
   do. Some researchers include Louis Herman, Mark Xitco, John Gory, Stan
   Kuczaj, Lori Marino, Diana Reiss, Adam Pack, and many others.

Tool use and culture

   In 1997, tool use was described in Bottlenose Dolphins in Shark Bay. A
   dolphin will stick a marine sponge on its rostrum, presumably to
   protect it when searching for food in the sandy sea bottom. The
   behaviour has only been observed in this bay, and is almost exclusively
   shown by females. This is the only known case of tool use in marine
   mammals outside of Sea Otters. An elaborate study in 2005 showed that
   mothers most likely teach the behaviour to their daughters. Subsets of
   populations in Mauritania are known to engage in interspecific
   cooperative fishing with human fishermen. The dolphins drive a school
   of fish towards the shore where humans await with their nets. In the
   confusion of casting nets, the dolphins catch a large number of fish as
   well. Intraspecific cooperative foraging techniques have also been
   observed, and some propose that these behaviors are transmitted through
   cultural means. Rendell & Whitehead have proposed a structure for the
   study of culture in cetaceans, although this view has been
   controversial (e.g. see Premack & Hauser).

Sexuality and reproduction

   The male has two slits on the underside of the body: one hiding the
   penis and further behind one for the anus. The female has one genital
   slit, housing the vagina and the anus. A mammary slit is positioned on
   either side of the female's genital slit.

   Courtship behaviour of the male includes clinging along to that female,
   posing for the female, stroking, rubbing, nuzzling, mouthing, jaw
   clapping, and yelping. Copulation is preceded by lengthy foreplay; then
   the two animals arrange 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.

   The gestation period is 12 months. The young are born in shallow water,
   sometimes assisted by a "midwife" (which may be male). A single calf is
   born, about 1 m (3 ft) 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, the males a bit later, at age 10-12.

   Janet Mann, a professor of biology and psychology at Georgetown
   University, argues that the common same-sex behaviour among male
   dolphin calves is about bond formation, and benefits the species
   evolutionarily. She cites studies showing that dolphins later in life
   as adults are bisexual, and the male bonds forged from homosexuality
   work for protection as well as locating females to reproduce with.

   Male Bottlenose Dolphins have been observed working in pairs to follow
   and/or restrict the movement of a female for weeks at a time, waiting
   for her to become sexually receptive. The same pairs have also been
   observed engaging in intense sexual play with each other.

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
   through charges; indeed, dolphin 'mobbing' behaviour of sharks can
   occasionally prove fatal for the shark. The Orca may also prey on
   dolphins, but this seems very rare.

   Swimming in packs allows dolphins to better defend themselves against
   predators. Bottlenose Dolphins either use complex evasive strategies to
   outswim their predators or they will batter the predator to death.
   Bottlenose Dolphins will also aid their injured by holding injured
   dolphins above water for air.

Conservation

   Bottlenose Dolphins are not endangered. Their future is currently
   foreseen to be stable because of their abundance and high adaptability.
   However, some specific populations are threatened due to various
   environmental changes. For example, the population in the Moray Firth
   in Scotland is estimated to consist of around 150 animals and to be
   declining by around 6% per year due to the impact of harassment and
   traumatic death, water pollution and reduction in food availability.
   Less local climate change such as increasing water temperature may also
   play a role.

   In U.S. waters, hunting and harassing of marine mammals is forbidden in
   almost all circumstances. The international trade in dolphins is also
   tightly controlled.

Bottlenose Dolphins and humans

   K-Dog, trained by the US Navy to find mines and boobytraps underwater,
   leaping out of the water
   Enlarge
   K-Dog, trained by the US Navy to find mines and boobytraps underwater,
   leaping out of the water

   Bottlenose Dolphins are still occasionally killed in dolphin drive
   hunts for their meat or because they compete for fish. Bottlenose
   Dolphins (and several other dolphin species) often travel together with
   tuna, and since the dolphins are much easier to spot than the tuna,
   fishermen commonly encircle dolphins to catch tuna, sometimes resulting
   in the death of dolphins. This has led to boycotts of tuna products and
   a "dolphin-safe" label for tuna caught with methods that don't endanger
   dolphins.

   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.

   The military of the United States and Russia train Bottlenose Dolphins
   as military dolphins for wartime tasks such as locating sea mines or
   detecting and marking enemy divers. The USA's program is the U.S. Navy
   Marine Mammal Program, located in San Diego, California.

   In the town of Laguna in south Brazil, a pod of Bottlenose Dolphins is
   known to drive fish towards fishermen who stand at the beach in shallow
   waters. One dolphin will then roll over, which the fishermen take as
   sign to throw out their nets. The dolphins feed on the escaping fish.
   The dolphins were not trained for this behaviour; the collaboration has
   been going on at least since 1847. Similar cooperative fisheries also
   exist in Africa, and have been reported through recorded history.

   A dolphin with an extra set of fins was found in Wakayama, Japan on
   October 28, 2006. Scientists are researching and have found that they
   may be the remains of hind legs. The dolphin is alive and will go
   through X-Ray and DNA tests.

Bottlenose Dolphins in fiction

     * The popular television show Flipper, created by Ivan Tors,
       portrayed a Bottlenose Dolphin in a friendly relationship with two
       boys, Sandy and Bud; a kind of sea going Lassie, Flipper understood
       English unusually well and was a marked hero: "Go tell Dad we're in
       trouble, Flipper! Hurry!" The show's theme song contains the lyric
       no one you see / is smarter than he. The television show was based
       on a 1963 film, and remade as a feature film in 1996 starring
       Elijah Wood and Paul Hogan, as well as a television series running
       from 1995-2000 starring Jessica Alba.

     * Ensign Darwin was a Bottlenose Dolphin crew member of seaQuest on
       the television series seaQuest DSV. Thanks to an invention by Lucas
       Wolenczak ( Jonathan Brandis), Darwin could communicate verbally
       with the crew. Darwin was not played by a real dolphin; it was an
       animatronic.

     * Bottlenose Dolphins have appeared in the film adaptation of The
       Hitchhiker's Guide to the Galaxy as well as the novel and one of
       its sequels, So Long, and Thanks For All the Fish. The dolphins are
       very intelligent creatures who tried in vain to warn humans of the
       impending destruction of Earth before making their own escape.
       However, their behaviour was misinterpreted as playful acrobatics.
       In particular, dolphins are noted to be the second most intelligent
       species on the planet Earth, ahead of humans, who ranked third.

     * The science fiction video game series Ecco the Dolphin stars Ecco,
       a young adult male Bottlenose Dolphin. The series also features
       societies of sapient cetaceans, time travel, and malevolent space
       aliens.

     * Zeus and Roxanne, an HBO TV movie about a female Bottlenose Dolphin
       (Roxanne) and a male dog (Zeus) becoming friends. The film stars
       Steve Guttenberg and Kathleen Quinlan.

     * In David Brin's series of Uplift Universe novels, one of the two
       species that humans have uplifted to sentience are the Bottlenose
       Dolphin (the other species is the chimpanzee). Also, a Bottlenose
       Dolphin named Akeakamai is a central character in his book Startide
       Rising.

   Factual descriptions of the Bottlenose Dolphin date back into antiquity
   - the writings of Aristotle, Oppian and Pliny the Elder all mention the
   species.

   Retrieved from " http://en.wikipedia.org/wiki/Bottlenose_Dolphin"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
