Dolphins
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Have you ever wondered why dolphins have been named one of the most intelligent animals, only second to apes and chimps? It is because dolphins have an extensive communication system. Dolphins are not only able to communicate with each other by means of clicks, whistles, squawks, squeaks, and other various sounds, but they are also able to connect with and understand humans. A dolphin also has a rare and amazing sonar system. Their system is so advanced that the United States Navy has been working with dolphins for years; studying them in order to produce higher quality sonar for submarines and naval ships (Pfeffer14-15).
Dolphins are marine mammals and part of the whale family. They are found in all four of the worlds oceans. Of the forty or so species of dolphins, some even live in rivers and lakes. Like their fishy neighbors, dolphins travel and hunt in organized groups. These groups are called pods. (Quick Facts) Dolphins are a generally friendly animal which makes it very easy for scientists and trainers to study and teach them.
Dolphins brains have areas for visual imagining only about one-tenth of the size of humans, but their “sound” imagining about ten times the size of a humans(Lilly). It is because they are developed this way that dolphins rely on sonar. Sonar stands for sound navigation ranging. It is a system which a dolphin transmits sound at an object, and the reflected echo the dolphin receives back can tell the dolphin the location of an object (Cerullo 40).
The form of sonar that is particular to a dolphin is called echolocation. In the deep, dark, murky waters of the ocean it can be hard for a dolphin to see and hunt. Since their eyesight is not very sharp they use their sense of echolocation. They send a series of clicks from their air sacs to their melon, an oily jelly filled “forehead”. From the melon, a dolphin can aim and direct the sound waves at a desired object. When the wave hits the object, it is transmitted back at the dolphin as an echo. The echo then travels through the dolphins lower jaw, then to its ear, and eventually hits its brain (Pfeffer 14-15). From the echo that the dolphin receives it can determine the location, shape, speed, size, texture, and density of any object or animal (Cerullo14).
From this sonar, a dolphin can locate objects as small as a pea (Pfeffer 19). Trainers test this remarkable skill by covering the dolphins eyes with rubber suction cups. The trainer then proceeds to throw an object into a large tank for the dolphin to find. Most dolphins can find a three inch ball from over 300 feet away establishing dominance. They use their teeth to make parallel scratches, called rake marks (Cerullo 14).
A dolphins sonar is so precise that they can actually tell the interior of an object. They can tell the difference right away between aluminum and tin cans. They can also tell if a fish is dead or alive from hundreds of feet away (Pfeffer 19). This “x-ray vision” is so intense that a trainer at Dolphin Reef in Israel entered a dolphin pool, and a dolphin circled her over and over excitedly. The dolphin then repeatedly aimed sonar at her abdomen. The woman found out one week later that she was three weeks pregnant (Cerullo 15). The dolphin could sense that the woman was carrying a child. There have been many other cases where dolphins act as a live sonogram for pregnant women.
Echolocation is not the only thing special to a dolphin. Dolphins have a unique and advanced system of communication. Dolphins are almost constantly being vocal (Dolphin Comm.). Each of their wide variety of sounds means something different. It all fits into the language of the dolphin. A dolphin makes sound by pushing air back and forth between air sacs in the nasal cavity just below its blowhole (Pfeffer 9). Most sounds that dolphins make we cannot hear (Cerullo 16). The sonar clicks they make are up to frequencies ten times those heard by human beings (Dolphin). The sounds that we can hear are the groans, barks, yaps, squeals, squawks, mews, and whistles (Cerullo 16). These are the sounds that give humans an insight into dolphins emotions.
Dolphins use different sound when showing different emotions, just like humans. Sounds that associate aggression with dolphins are barks and squawks. Along with these sounds, aggression is communicated by an open mouth, exaggerated movements, jaw clapping, and inverted swimming (Dolphin Comm.). Aggression is also produced in buzzing click-trains (DRC). During playful activities dolphins make squeaking sounds (Dolphin Comm.). The higher pitch sounds are associated with happier times. Sounds that dolphins use during sexual interaction are the chirps (Dolphin Comm.). When a dolphin is upset it will make loud popping noises. It will even clap its jaw and slap its tail, sometimes even hitting the water with its entire body (Pfeffer 22).
Dolphins formulate these sounds by pushing air back and forth between air sacs in the nasal cavity located directly below the blowhole (Pfeffer 9). The tissue structures in the air sacs slap together to produce the noises, much like how a trumpet players lips react to his instrument (Dolphin Comm.). These sounds are produced at an average of 300 sounds per pulse (Dolphin Comm.).
The most dominant sound a dolphin can make is a whistle. The whistle is the key to the language of dolphins. It is definitely the most important vocalized sound that a dolphin can produce. Every dolphin has its own distinctive signature whistle (Cerullo 40). The whistle is equivalent to a humans name or fingerprints. The whistle is so important that a mother dolphin will whistle to her calf almost continuously for several days after giving birth. This is so the calf can learn right away to identify its mothers whistle in case they become separated (Dolphin Comm.). It only takes dolphins a few days after birth to develop their own signature whistle (Cerullo 22). The gender of a dolphin really helps in the process of developing a whistle. A male calf shapes its whistle to resemble its mothers, whereas a female calf creates a variation of its mothers (Cerullo 22). The whistle helps a dolphin connect with their pod (Cerullo 16).
Pods are very protective of their members. Within a pod, a whistle can let the rest of the pod know who is around, where they are, and perhaps, something about their mental state (DRC). If the pod does not recognize the sound of the approaching whistle, the vocalizing dolphin will either be completely ignored, or the pod may become aggressive towards the impending dolphin (Cerullo 16). When a young calf or sometimes even an older dolphin is lost from the group they will whistle continuously until it gets the recognition whistle back from its pod (DRC).
The ocean is a big