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LIVING SANIBEL: Understanding the bottle-nosed dolphin

By Staff | May 28, 2010

Bottle-nosed Dolphin (Tursiops truncatus) Other names: flipper, porpoise,

dolphin, common bottlenose dolphin / Status: Fla. =stable, IUCN=LC / Life

span: to 25 years / Length: 7.5-9.5 ft (2.28-2.9 m) / Weight: 330-1,400 lb

(150-650 kg) / Reproduces: in the back bays and estuaries / Found: Bay Bay,

Gulf.

Any visitor to Sanibel and Captiva would be hard pressed not to spot a

bottle-nosed dolphin over the course of a week’s stay. The dolphin is often

observed swimming in the gulf just off the beaches or can be spotted inshore

while kayaking or canoeing through the “Ding” Darling Refuge, in Tarpon Bay,

or along the bay side of Captiva. The dolphin can also be readily observed

from the Causeway, where it gathers to feed in the huge tidal flows along

the Caloosahatchee River. It is always a delight to watch and shows little

fear of man.

Worldwide there are 32 different species of toothed whales, the family

(Delphinidae) to which this dolphins belongs. The largest member of this

extensive family is the orca, or killer whale, which can reach lengths of 30

feet and weigh as much as 9,000 pounds. The orca will attack and eat

dolphins given the opportunity.

The dolphin is an extremely social animal, living in groups of 15 to 100

animals called pods. Several larger pods have been identified with as many

as 1,000 members.

The dolphin has a unique and special relationship with man. Tales of

bottle-nosed dolphins saving drowning sailors date back to Greek times,

although recent studies indicate that this may be part of an instinctive

behavior.

With a brain size larger than ours, the bottle-nosed dolphin has been

studied extensively for decades. Highly intelligent, it has been trained to

perform in places such as Sea World in Orlando, as well as to carry out

tactical exercises including the detection of sea mines and enemy divers for

the U.S. Navy. In some parts of the world the dolphin has actually learned

to cooperate with local fishermen, driving schools of fish into their nets,

then taking the escaping fish as a form of payment for services rendered.

The dolphin has a wide array of sounds and noises, including many in ranges

far above the capacity of the human ear. An interesting study is being

conducted by neurologists at Caltech University in California where

scientists have verified that the dolphin has distinctly shaped brain cells

(called von Economo neurons), which are found only in the great apes,

elephants, and the whales. This may be biological evidence for behaviors

that were once considered to be strictly human. These elongated neuron cells

appear to be responsible for language, as well as empathy, trust, guilt,

embarrassment, love, and humor.

Another amazing though seldom discussed fact about the bottle-nosed dolphin

is its highly unusual sexual activity. Like humans, the dolphin is one of

only a handful of species that has no set breeding or calving season, but

mates and procreates any time of the year. Numerous studies of both wild and

captive bottle-nosed dolphins have verified that this marine mammal engages

in group sex, bisexuality, cross-species sex with the spotted dolphin, and

homosexual activity. Some male pairs appear to partner for life, while the

female dolphin, who may raise up to 10 calves in her breeding lifetime, will

have a different father for every calf she births. Recent evidence indicates

that as many as 1,500 species of wild animals engage in some form of

homosexual or bisexual activity, including giraffes and chimpanzees. Some of

this behavior may be related to social bonding and establishing dominance.

The dolphin eats mostly fish, but also takes squid and octopus. Along the

west coast of Florida its predominant prey is mullet, which it stun with its

powerful tail, flipping the fish high in the air, then swimming back to dine

on it. Several dolphins will sometimes be seen working together as a team to

corral schools of striped mullet in a behavior similar to that of lion

prides or wolf packs. High-frequency vocalizations help the dolphins

coordinate these mullet hunts. Although the temptation exists to feed this

marine mammal, it is never advisable. It can make the dolphin dependent on

humans for food and can lead to it becoming entangled in cast nets and

fishing line, resulting in injury or sometimes death. Another concern is

that the dolphin can and will bite. Feeding any wild animal, from shark to

alligator, is not advisable.

In the wild, the dolphin has several natural predators. In Australia and New

Zealand scores of bottle-nosed dolphins display scarring from past shark

attacks. In Florida the bottlenose has been known to be killed by bull,

tiger, and hammerhead sharks, as well as killer whales. It is also

infrequently killed when it gets entangled in crab-pot lines and gill and

trawl nets. Water pollution, especially raw sewage that can bring on

diseases, nutrient-rich dead zones from the overuse of fertilizers, and red

tides also take their toll. The dolphin is also known for stranding itself,

en masse, on beaches, though no one to date has been able to explain this

bizarre and often fatal behavior. It is still killed and eaten in Japan and

parts of China but is protected throughout most of its range.

One of the most difficult things for a self-centered species such as

homosapiens to come to grips with is the concept that we may not be the most

advanced or sophisticated species on the planet. While it is obvious that

we, as tool makers and tool users, can out-compete and hence eradicate the

entire world population of bottle-nosed dolphin, it is another thing

entirely to admit that the dolphin has a better world in which to live. It

doesn’t make tools because in its environment it doesn’t need them. It has

far more habitat than humans because the oceans cover more than 70 percent

of the globe. It has no gravity to contend with, ample food, few natural

predators, a complex and rich social environment, and in all probability

some kind of language, though we have yet to decode or understand it.