Anatomy:
- They have a sleek, streamlined, fusiform body
- The pectoral flippers have the skeletal forelimbs of terrestrial mammals, rigidly supported by connective tissue and with thick cartilage pads between the bones. They are used to steer and, with the help of the flukes, to stop. Also the blood circulation in the flippers helps adjusting the body temperature
- The flukes are the lobes on the tail and they are flattened pads of tough, dense, fibrous connective tissue, completely without bone or muscle. The up and down movement of the tail is what propels them through the water
- The dorsal fin is like the flukes, with no bones and composed with the same tissue. It acts as a keel, helping stabilize the dolphins as they swim, though it's not really essential because some species lack it. It's often falcate (curved back), although the shape is quite variable and is located at the center of the back
- The teeth are conical and interlocking, designed for grasping, but not chewing food. The number varies considerably among individuals, even in the same species
- The eyes are located on the sides of the head, near the corners of the mouth. Glands at the inner corners of the eye sockets secrete an oily, jellylike mucus that lubricates the eyes, washes away debris, and probably helps streamline a dolphin's eye as it swims. This tearlike film may also protect the eyes from infective organisms
- The ears , located just behind the eyes, are small inconspicuous openings, with no external pinnae (flaps)
- The nose is a single blowhole, located on the dorsal surface of the head, covered by a muscular flap that provides a water-tight seal. When relaxed it's in a closed position
Senses:
- They have a well-developed, acute sense of hearing. Dolphins have a highly developed auditory cortex of the brain with 67,900 or more cochlear fibers, twice as the humans. They can hear frequencies from 1 to 150 kHz, while the humans is .02 to 17 kHz
- Most of the reception of the sound isn't directly done by the ear. The lower jawbone has a fat-filled cavity that conducts the sound through the skull. The specialized anatomy of the ear allows dolphins to localize sounds under water effectively and also adjust pressure when they dive
- Their eyesight is sharp both in and out of water. Their complex, well equipped eyes allows not only the correction of the cornea when changing media, but have both binocular and monocular vision under water and the ability to see in both dim and bright light
- Their sense of smell is very poor, as it should be expected since the blowhole remains closed underwater. The olfactory nerves as well as the olfactory lobe in the brain are missing
- The sense of taste is not well studied, but they do have taste buds and are able to detect salty, sweet, bitter and sour tastes
- Their skin is very sensitive to touch, but it's unclear if there are also pain and temperature receptors in their skin. The most sensitive areas to touch are around the blowhole and the eyes and the upper and lower lips, near the corner of the mouth, while the snout, melon and lower jaw are somewhat less sensitive and the skin on the back and tail stock are the least sensitive areas of the body
Ecolocation:
Communication:
Bottlenose DolphinSpecie: Tursiops truncatus
Shape: They have a well-defined rostrum (snoutlike projection), usually about 7-8 cm (3 in.) long, marked by a lateral crease
Size and Weight: Adults can reach 6-13 ft and weight 150-650 kg, with males being slightly bigger than females and coastal families being smaller than offshore ones
Coloration: Dark grey or gray-green on top and light grey to nearly white or pinkish on the bottom. Some of the older dolphins can show spots along their sides and on their bellies
Diet: A wide variety of fish, cephalopods and crustaceans, eating approximately 4% to 9% of their body weight in food per day
Habitat: They live in the Atlantic, Pacific and Indian oceans, inhabiting pelagic zone as well as harbors, bays, lagoons, gulfs, and estuaries. They prefer warm to tropical waters
Life Span: They can live from 30 to 50 years, females usually having longer lives
Reproduction: The females become mature at 5-12 years old, while the males at 9-13. They don't mate for life and only the females raise their young
The females are receptive during most of the year, but the mating peak varies with the location
The females only have a calf every 3-5 years and only one at a time (twins are possible but it's a very rare occasion). The gestation takes 11-12 months. The females move to quieter areas to give birth, which usually takes 20-30 minutes
Sometimes an assisting dolphin stays close to the mother and calf, being either male or female. Often that's the only one the mother allows near her baby
The calf is 42-52 inches long and weights around 20kg and in the first few days after birth the dorsal fin and tail flukes are flaccid and pliable. They are darker than the adults and have several vertical, light-colored lines on their sides from "fetal-folding", which fade in the following 6 months
The calves are nursed until their 12-18 months old, but they will stay with their mothers until they mature or even longer
Predators: Large sharks and killer whales
Behaviour:
Note: They're the most aggressive of dolphin species
Dusky DolphinSpecie: Lagenorhynchus obscurus
Shape: They have a short, dark beak and gently sloping forehead. Their bodies ae compact and their fins tall
Size and Weight: Adults are between 5 to 7 ft long and weinght between 50-90 kg
Coloration: Their upper sides are predominantly dark or blue-black, but there are white or pale-grey blazes along their sides and on their belly. The fins have a light grey area on the rear half
Diet: Fish and cephalopods
Habitat: Southern Hemisphere, in costal areas around South America, South Africa, and New Zealand
Life Span: Between 20 to 25 years (estimated)
Reproduction: They reach maturity around 7-8 years old (estimated) and are promiscuous, with the males competing to have access to the females, with no bonds apparently formed besides the strong social cohesion within the school
The mating usually takes place during the spring. The gestation lasts 11 months, being June to August the peak months of birth. The females only give one birth to one babe every 2-3 years
The young weight around 5kg and measure between 22 and 28 inches at birth......
Predators: Killer whales and some shark species
Behaviour:
Note: They are one of the most acrobatic of dolphin species and often easy to approach
http://rosmarus.com/dolphfaq.htmhttp://marinebio.org/species.asp?id=365http://en.wikipedia.org/wiki/Dusky_Dolphinhttp://en.wikipedia.org/wiki/Bottlenose_dolphinhttp://www.seaworld.org/infobooks/Bottlenose/home.htmlhttp://www.cms.int/reports/small_cetaceans/data/l_obscurus/l_obscurus.htm
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