/// Dolphins in Bunaken

07 Nov / 2011
Author: Two Fish Blog Tags: Comments: 0

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DOLPHIN_1It is common to see dolphins in Bunaken National Park. There are 28 different types of whales and dolphins that have been seen in the park, however they are shy animals and most of the times we see them in the surface rather than diving.

When we do see them then often it is in very large schools of 50-100+ animals, as in the photo on the right.

Here a little bit more information about these amazing animals!

Introducing Dolphins

They are mammals of the order Cetacea and the families Plantanistidae and Delphinidae and include about 50 species.  All have a beak like snout and sharp, conical teeth.

Most dolphin species are about 6 ft in length, the males averaging 4 to 8 in longer than females.  The largest is the killer whale, which can be 19-22ft long and weigh between 8000-10000lbs.

Dolphins feed on live food and are predators, except when trained otherwise in captivity.  The primary food is fish, mostly things like herring, mackerel, and sardines.  Some species seem to prefer squid, occasionally, shrimp and other crustacean are consumed, and even mollusc shells have been found in their stomach contents.

Physiology
DOLPHINThe body is sleek and smooth and the hairless skin is rubbery to the touch.  Most species have jaws that protrude into a beak like snout.  Above the upper jaw is a large mass of fat and oil-containing tissue forming the so-called “melon” that looks much like a bulging forehead.

The anterior appendages contain the skeletal remnants of five digits that form the flippers, which the animal uses primarily as stabilizers, although occasionally in an oar like fashion.  The hind appendages are virtually absent and consist of a pair of small pelvic bones, deeply embedded in the connective tissue at the base of the tail.  The dorsal fin is formed from subcutaneous dermal tissue and is not movable by muscle action.  The caudal, or tail, fin is also primarily dermal in origin, rather than skeletal, and consists of a pair of horizontally extending flukes.

The locomotion of dolphins is typical of the whale. The main thrust comes from vertical oscillations of the tail and flukes, and most species tested are capable of sustained swimming speeds of up to 18.6 mph and they jump at this high speeds travelling 30 ft or more.  Their normal “cruising speed” is about 23 to 25 mph, and if they are bow riding, they have been known to get up to 30mph (bow riding is when the dolphin rides the front bow wave produced by a boat/ship).

Because dolphins are mammals, they must breathe air and maintain a high body temperature.  The  internal temperature, between 97.9 deg to 99 deg F, is acheived by a thick layer of blubber under the skin.  Air is breathed through blowhole, situated almost directly on top of the head.  The dolphin normally come to the surface to breathe about every two minutes,  and each breath consists of a short, almost  explosive exhalation, followed by a slightly longer inhalation.  Dolphins can hold their breath for up to several minutes and are capable of rapid and deep dives of more then 1,000 ft.

Reproduction
Mating normally occurs during the spring months, like with most animals, with the male-female pair exhibiting courtship for some time prior to the actual mating.  A female dolphin has to carry her baby (calf) for 11-12 months.  The calf is delivered normally tail first, and the newborn is capable of swimming and breathing within the first minutes.  The calf will follow its mother closely, and suckling takes place frequently, with the mother tolling slightly and the calf nuzzling the mammary area.  The dolphin’s two mammary glands open into a pair of sacs on either side of the anal opening, and the calf’s beak fits into the openings on the sacs.  The nipple is grasped between the upper jaw and the tongue, and muscular contractions by the mother literally squirt mil into the calf’s mouth.  Nursing may continue for as long as 12 to 18 months after birth, although weaning is probably slowed or inhibited in captive animals.

Communication
Dolphins are extremely and almost constantly vocal.  They are capable of two kinds of sounds.  A specialized mechanism in the nasal passages just below the blow-hole enables them to emit short, pulse-type sounds.  These sounds, called clicks, can be produced in such rapid succession as to sound like a buzz or even a duck like quack.   The clicks are used as a form of sonar, in which echoes of sounds from surrounding objects enable the animals to detect obstacles, other dolphins, fish, and even tiny bits of matter in the water.

Pat, Bunaken

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