Species distinctions: Bottlenose dolphin:
Weight: 200.0 to 370.0 kg ( 440.0 to 814.0 lbs)
Length: n/a
Gestation period: 310 to 360 days ( 10 to 12 months)
Number of young: 1 calf
Life-span: 25 years (natural death)
Diet: fish
Distinctive qualities: sociable and may be found in pods of 10 to 20 which are close to one another; extremely playful; texture of skin offers minimum resistance to the water, providing for fast movement; communicates constantly many sounds; will attack sharks.

Species distinctions: Ganges dolphin:
Weight: n/a
Length: 2.0 to 3.0 m ( 6.5 to 10.0 ft)
Gestation period: 248 to 280 days ( 8 to 9 months)
Number of young: 1 calf
Life-span: n/a
Diet: fish
Distinctive qualities: sociable, found in pods of ten to twenty; completely blind after years of evolution, with no true explanation, except that it lives in muddy rivers; live in fresh water; use ultrasonics to navigate and fish, and to avoid being caught by nets; elongated mouth with slender jaws and 133 teeth, which form a sort of saw.

Species distinctions: Killer whale:
Weight: 900.0 to 4000.0 kg ( 1980.0 to 8800.0 lbs)
Length: up to 9.0 m (30.0 ft)
Gestation period: 360 days ( 12 months)
Number of young: 1 calf
Life-span: 20 years (natural death)
Diet: fish, penguins, seals, blue whales (by team work), porpoises, sea-lions
Distinctive qualities: largest of dolphins; a vicious carnivore, which will attack and eat a blue whale; lives in pods of 5 to 20, surfacing frequently to breathe; use ultrasonics to communicate; seems to have no initiative to harm homo sapiens.

Species distinctions: Pilot whale:
Weight: 800.0 to over 3000.0 kg ( 1750.0 to over 6500.0 lbs)
Length: 4.8 to 8.5 m ( 15.0 to 28.0 ft)
Gestation period: 1 year
Number of young: 1 calf
Life-span: 50 years (natural death)
Diet: cuttlefish
Distinctive qualities: forehead bulges out above mouth/beak, which accommodates the organs used in ultrasonic communication; may be found in pods of 50 to several hundred (even a several thousand); an old male may act as leader, but pilot whales apparently will follow any one of their pod members, even a wounded whale, which will be followed blindly by all others- if one makes a navigation error, many whales find themselves beached in shallow water.

Ultrasonics - echolocation: The most notorious characteristics of dolphins which are usually observed is their playfulness and their intelligence, which often sets them apart from other organisms studied by homo sapiens. However, their reliance upon ultrasonic waves is not discussed as often, where many humans are not aware that the dolphin employs a system of ultrasound which has been found to be four times more powerful than that used by humans. The dolphin is sensitive to sounds and it uses such sounds perhaps more effectively than any other organism, although the bat and the elephant possess their own well-developed sense of sound and its many uses.

Dolphins are known to emit an array of sounds and noises beneath the surface: they are known to sound moans, cries, whines, barks, squeaks, whistles, yelps, grunts, clicks, rasps, mews, squawks, "rusty hinge" and "motor boat" sounds. Such sound may be emitted as low frequencies of the homo sapiens audible range to ultrasonic wavelengths, which are ten times higher in pitch than sounds which are audible. With ultrasonic sounds, the dolphins are able to navigate, communicate with one another in pods, and locate prey, mostly at night, in darkness, or when acute sight lacks in the gathering of surrounding information. It was found in studies that if the dolphin is placed in a tank of colourless water and they are familiar with the walls and the tank size, echolocation is not used excessively. However, if the animal is unsure, many clicks of ultrasound waves are emitted. In communication, studies have discovered some of the particular sounds used by dolphins to communicate particular messages: a short, flat whistle proceeded by a high-pitched, muscle whistle is a distress signal; a yelp is a mating call; barking is the expression of angry dolphins; and the whistles from a mother are always answered by the offspring.

The echolocation of the dolphins is like that of bats, however the dolphins are marine mammals with specially shaped heads to focus on objects, which does not change the general concept of echolocation: sound waves of high frequency are emitted, which reflect off an object or prey and upon return, the dolphin is able to process the information and even receive "pictures", also measuring the time it took for the sounds to be send and returned. From the waves they direct out from their body, dolphins can derive the location, distance, speed, direction, and size of the object, which are often fish who are unaware that they are made to be a target. The sonar involved increases the pulse rate of the prey, as well as penetrating it, similar to x-rays used in medicine: the sonar of the dolphins also penetrates humans to display the skeleton just as it is able to penetrate through a pregnant female, allowing the dolphin to perceive the image of the skeleton of both mother and fetus, as well as the heartbeat of the fetus, much like the ultrasounds used to do the same for humans.

The echolocation system employed by dolphins has been of interest for many years, where there was curiosity regarding the origin of the ultrasonic "clicks" and the ability for dolphins to perceive and process the waves and their information. These clicks are not constant in loudness nor quality and are found in many forms of sounds, such as whistles or moans, however it was realized that none of the changes in sounds produced bubbles. Because there were no bubbles formed, it was determined that sonar signals do not come from the blow hole. However, dolphins possess no vocal chords, which leads to the belief that the ultrasound waves are produced from the snout as continuous chains of vibrations at approximately 3000.0 to 200000.0 Hz, produced as air is blown through the nasal passage and over two, flap-like structures inside the blowhole. The sounds are then manipulated by tension increase and decreased of the nasal flaps and by maneuvering the plugs in the airway and blowhole. To perceive sounds, a form of beak (known as the rostrum) which acts like a "sonic brush" when another organism is near, which works for short distances. For long distances, it is possible dolphins use an organ common to toothed whales like themselves: a hollow, located in the frontal region of the head, containing wax-like fat consisting of a tissue network that may amplify and magnify sound at a higher rate than the surrounding tissue. To focus, it uses successive reflections and sonic waves that occur within a given incidence. The origin of the clicks may be attributed to a larynx-like muscle, where the tongue plays no part, producing sounds at rates between 800.0 to 1200.0 clicks per second, faster than could possibly be produced by muscles or any naturally occurring vibrating membrane.

Dolphins are capable of perceiving sounds of 200000 Hz by use of their ears, which are merely openings found behind the dolphin’s eyes, leveled with the skin, which may be accredited to water pressure. Echoes are emitted and received through the intermediary of the highly sensitive lower jaw, which contains fatty, liquid-like tissue and major nerve terminals that connect to tissues, all of which transmit sound to the inner ear, where the cochlea is the same size as that of a human, but the acoustical nerve is larger with thicker contact fibers. This distinguishes the dolphin as a primarily audile organism, where it depends on sound to survive (as well as sight), also proven by the species of Ganges dolphins, who are blind and rely explicitly on sonar to locate prey and navigate, as well as avoid capture by nets. It has also been found that the auditory nerve, the eighth cranial nerve, of the dolphin is highly-developed and is the largest of cranial nerves, where in the cortex, the auditory center is enormously large and the ear modified for use in water. The sensory cells used to perceive the highest frequencies are large, each possessing their own nerve fiber, where humans only have connection with one fiber: it is similarly developed in relation to other organisms that depend on their sense of hearing to survive. This sonar system is very important and is very sensitive, allowing the dolphin to even distinguish two fish from a distance of 4.6 to 5.5 m (15.0 to 18.0 ft). Experiments have shown that the dolphins are capable of detecting a 7.5 cm (approximately 3.0 in) target at a distance of 110.0 m (360.9 ft) in cloudy water, which poses the following question: how much time passes between the moment the dolphin emits an ultrasonic click and the moment at which the dolphin receives the reflected click which allows the dolphin to process the information about the target? The answer may be derived by acquiring the use of mathematics and physics:

      t = d / v             

                                         = (2.2 x 10² m) / (1.4 x 10 ³ m/s)

 = 0.16 s

From using such methods, other such incidents may be measured and calculated. Dolphins are known to associate by their own free will with homo sapiens, where they will chase sharks away in both dolphin and human emergencies, as well as aiding in the surfacing of drowning victims. The reason is not completely understood thus far, however it is believed to be due to the fact that dolphins and humans are subjected to similar issues: though it may not seem possible, dolphins, too, can drown.

"Dolphin therapy" is becoming extremely popular, where interactions with dolphins seem to help those with illnesses or diseases, as well as individuals with Down Syndrome and autism. Scientists claim the ability for dolphins to help "heal" humans is found in the boost of production of P cells (fighting cells) in cancer and AIDS patients which are triggered by dolphin encounters. It is also theorized that it may be due to the ultrasound which penetrates tissue: the waves, which can resonate the swim bladder of a fish and cause it to become disoriented, may also generate minute changes in diseased (or non diseased) human cells. However, other doctors and scientists believe the change in health to be due to a sense of "well-being" patients feel when with dolphins, all of which are very possible.