WELL, THIS IS NOT QUITE A BOTTLENOSE DOLPHIN, BUT IT IS THE LARGEST OF ALL THE DOLPHINS--A KILLER WHALE! Addendum A. BOTTLENOSE DOLPHINS
Dolphins, killer whales, porpoises, blue whales, sperm whales, gray whales, humpback whales, and all the other species of whales all belong to the scientific group/order called Cetacea. This group has forelimbs modified into flippers, a horizontally flattened “tail,” 1 or 2 nostrils at the top of the head (called the blowhole) modified for breathing, and no hind limbs. There are 2 general groups of cetaceans: those with teeth and a single blowhole, called the Odontoceti, and those having a specialized structure, called the baleen, which is used for filtering small food out of the water, called the Mysticeti.
The latter group contains the largest of the whales, called the blue whale, as well as the gray and humpback whales.
At this exhibit, called Rocky Point Preserve, is one of the “toothed whales,” the Bottlenose Dolphin. The toothed whales include all the ones we call dolphins and porpoises, as well as the killer whale and the sperm whale (which is the largest of the toothed whales). In the dolphin group, there are at least 36 species/kinds of “dolphins,” including the bottlenose, pilot whales, and killer whales.
Whales probably arose 50 million years ago, from some primitive mammal (now extinct) that “tried out” the seas. 2 small rod-shaped pelvic bones, buried deep in the body muscle of the toothed whales, may be the remnants of the hind limbs of these primitive mammals. The modern forms of these toothed whales first appear in the fossil records 5-7 million years ago. Current biochemical and genetic studies indicate that some ungulates, especially the hippopotamus, may be the closest living terrestrial relatives.
Bottlenose dolphins, of which there are 2 distinctly separated kinds (Indo-Pacific and the much more common), live in temperate and tropical waters worldwide. They are usually limited to waters that vary between 50-90 degrees F. The common bottlenose is found in the Pacific from northern
There are 2 forms of the bottlenose dolphins: coastal and offshore. In general, the coastal ecotype seems to be adapted for warm, shallow waters with:
Smaller bodies
Larger flippers
Both of which suggest increased maneuverability and heat dissipation.
These frequent harbors, bays, lagoons, and estuaries.
The offshore type seems to be adapted for cooler, deeper waters: blood characteristics indicate that this form may be better suited for deep diving, and its larger body helps to conserve heat and defense against predators.
Bottlenose dolphins are not endangered. Estimates of population sizes include:
Eastern tropical Pacific—250,000
Western North Atlantic—30,000
Sizes:
v Between 6-12 feet in length, with weights between 300-1000 pounds.
v Adult males are slightly longer and considerably heavier than adult females
Body shape: fusiform type for streamlining and minimizing surface area to volume ratios.
Skin: smooth and “rubbery.” No hair nor sweat glands. The epidermis, or outer layer, is 10-20 times thicker than that of terrestrial mammals. The skin flakes and peels rapidly, so that a bottlenose dolphin’s outermost skin layer may be replaced as often as every 2 hours! This is almost 10 times faster than that of MAN.
Color: gray to dark gray on its dorsal/back, fading to white or lighter gray on its lower jaw and belly, providing a type of camouflage called “counter shading.” When viewed from above, the darker back blends with the dark depths, whereas when viewed from below, the lighter belly blends with the brighter sea surface. This is a response to predators.
Blubber: a layer of fat reinforced by fibrous connective tissue, making it an excellent insulating layer to reduce heat loss. It also contributes to the streamlined shape, stores calories. Fluctuates by season as well as with body size and health statu s.
Pectoral or Fore flippers: they contain the major skeletal structures of a land mammals fore limbs, but they are shortened and modified. These flippers are curved back and pointed at the tips. They are roughly about 20 inches long. The dolphins use these foreflippers for steering and braking. The blood circulation in these foreflippers also aid in adjusting for internal body temperatures.
Tail fluke: each lobe of a dolphin’s tail is called a fluke; thus, the tail is called the tail flukes. They are flattened pads of tough, dense, fibrous connective tissue but without bone, cartilage, or muscle. They measure about 24 inches each, so that the total spread of the tail flukes is about 20% of the body length. Longitudinal muscles of the back and narrow part of the body move the flukes up and down to propel the dolphin through the water.
Dorsal fin: in dolphins, this is falcate (curved back), located around the center of the back. It is made of dense, tough, fibrous connective tissue without muscles, bones, or cartilage. Although it is probably not essential, to those which have a dorsal fin, it probably lends to stability/balance; the narwhal and beluga whale do not have a dorsal fin.
Head: the rounded region of a dolphin’s forehead is called the melon. It contains fat and plays an important part of a dolphin’s echolocation.
Teeth: Conical and interlocking, designed for grasping food, but not for chewing. These dolphins have 18-26 on each side of the upper and lower jaws, for a total of 72-104 teeth. The teeth are not replaced.
Eyes: on the sides of the head, near the corners of the mouth. Glands at the corners of the eyes secrete an oily, jelly like mucous that lubricates the eyes, washes away debris, and probably helps the streamlining as it swims. Each eye moves independent of the other. The eyes provide acute vision, especially underwater. They see well in dim light, but probably are not able to discriminate colors in the blue end of the wavelengths of light.
Ears: small, inconspicuous openings, behind the eyes, with no external flaps.
Single opening called the blowhole, which has a muscular flap that provides a water tight seal when the dolphin is swimming underwater. The blowhole and areas around the eyes and mouth appear to be the most sensitive parts of the dolphin’s body.
A dolphin’s brain size relative to its body size is larger than many mammals of the same body size. A larger brain size is probably due to an increased size of the auditory regions to facilitate sound processing in echolocation. Guesses that large brain size indicate high intelligence are untested and disputed.
Hearing: dolphins have a well developed, acute sense of hearing. They have a greater and more acute hearing than MAN; the sound reception seems to occur through soft tissue and bone conduction rather than through the small, inconspicuous ear openings.
Taste: they do have taste buds, and they show preference for specific food fishes. However, the absence of the olfactory lobes in the brain indicate no have a sense of smell.
Swimming: 3-7 mph cruising speeds, with 18-22 mph maximum short bursts. They can swim fast enough at the surface to break free of the water, flying up and out of the waer and then back under in one continuous movement, which they generally repeat. This uses less energy than swimming at the same speed under water.
Breathing: single blowhole opening. Often see a mist of water being blown up into the air; this is not from water in the lungs, which it cannot tolerate, much like MAN. It is due to water that is collected on top of the blowhole, plus some water vapor condensing as the respiratory gases expand in open air. During each respiration, a dolphin can exchange more than 80% of its lung air. Exhaling and inhaling only takes about 0.3 seconds.
Diving: generally do not need to dive very deep to obtain food. Depending on area in which they live, they; normally dive to depths of 10-150 feet. They can dive to greater depths, as they have experimentally made dives to more than 2000 feet. The dives may last up to 10 minutes, with the maximum probably around 12 minutes. Adaptations for diving are: slowing of heart rate, shutdown of peripheral circulation, and presence of myoglobin.
Sleep: spend about 1/3 of each day sleeping, but during deep sleep, only one brain hemisphere is involved.
Echolocation: sense well developed, as the dolphins rely heavily on sound production and reception to navigate, communicate, hunt, and avoid predators in dark or limited visibility waters.
Ø Produce whistles and sounds that resemble moans, trills, grunts, squeaks, and creaking doors.
Ø Sounds vary in volume, wavelength, frequency, and pattern.
Ø Identity with a signature whistle. These are so distinct that a researcher can readily identify an individual dolphin by looking at their whistle shapes on a sonogram.
Ø To date, there is no evidence of a dolphin “language.”
Food: active predators, eating a wide variety of fish, squids, and crustaceans, like shrimps. They do show strong preference for certain species of food fishes, especially in an aquatic park like Sea World. They eat 4-6% of their body weight in food daily.
Social organization: live in fluid social groups. A pod is a group of unchanging composition. Establish dominance by raking: scratching one another with their teeth, leaving superficial lacerations that soon heal.
Reproduction: 5-12 years before sexual maturity. Breed throughout the year, with gestation lasting about 12 months, with calving averaging about once every 3 years. Calves are about 4 feet long, weighing 10-40 pounds. Nursing may last up to 18 months.
Longevity : probably live about 20 years in nature. Some live past 40 years at Sea World, with the oldest female being more than 50 years.
Sea World and
No comments:
Post a Comment