Dolphins are arguably the best known and loved of all the marine mammals. However, many aspects of the dolphins way of life still remain a mystery. Be that as it may, dolphins have been the subject of scientific research for decades and so at least there are some areas of dolphin behaviour that we do know of.
So, just what do dolphins do?
Dolphins use whistles and clicks to communicate with each other. It is not yet known how complicated this language is, but they undoubtedly recognise and respond to one another.
Dolphins usually mate in the spring and the summer, and the females give birth underwater to a single calf 10 to 12 months later.
Once the calf is born, it will suckle 3.4 liters of milk every day for 9 months or less. Baby dolphins do not have lips and since they are unable to suckle the nipple, they hit it with their rostrum (beak) until the milk is ejected. The dolphin mother will nurse her calf for at least 16 months, so she generally comes into breeding condition once every two to three years. Each time she does breed it is likely to be with a different male.
This kind of social help also extends to injured dolphins too. An injured dolphins cries of distress will summon instant aid from other dolphins in the vacinity. They will then try and carry or support the injured dolphin in the water so that it is able to reach the surface and breathe.
What do dolphins eat?
The worlds dolphin populations are made up from almost forty species varying in size from 1.2 m and 40 for the Maui's dolphin, and up to 9.5 m and 10 tonnes for the killer whale. They are found worldwide, mostly in the shallower seas of the continental shelf. So clearly, with this much variation within the dolphin family, you can expect the same variation in each species diet.
So, while some dolphins eat fishes like herring, cod or mackerel, others species will prefer to eat squids.
Of course, the largest of all the dolphin species - the killer whales - will also eat marine mammals like seals or sea lions and sometime even turtles.
On average, a dolphin with a weigh of 200 to 250 Kg will eat between 10 and 25 Kg of fish every day.
How do dolphins catch their food
As you can expect, various methods of feeding exist among and within species, some apparently exclusive to a single population. Fish and squid are the main food, but the false killer whale and the orca (the true killer whale) also feed on other marine mammals like seals. They have been known to eat penguins and even sea turtles!
Corralling is another method where dolphins chase fish into shallow water to more easily catch them. In South Carolina, the Atlantic bottlenose dolphin takes this further with "strand feeding", driving prey onto mud banks for easy access.
In some places, orcas come to the beach to capture sea lions. Some species also hit fish with their tails, stunning them and sometimes knocking them out of the water.
The clicks are directional and are for echolocation, often occurring in a short series called a click train. The click rate increases when approaching an object of interest. Amazingly, dolphin echolocation clicks are amongst the loudest sounds made by marine animals!
In 2011 researchers in the United States and Great Britain have been using a CymaScope to find out more - a CymaScope is an instrument which produces visible patterns from sound. They have found that part of dolphin communication consists of receiving and transmitting sound pictures. It is almost certain that to this ability is shared by the entire dolphin family.
Can humans communicate with dolphins?
Impressed with their large brains, Lilly performed many audio experiments in order to attempted to show that dolphins were communicating with each other. In an effort to enhance human dolphin communication, he began to use computers to translate human words into dolphin whistles and to send messages back. Unfortunately,much of his experimental work has never been published.
In one Lilly experiment, a woman lived in a pool with a bottlenose dolphin named Peter as her only companion for several months. Sleeping in a bed above the pool, she was ever on call. Communication attempts were often transing sessions, where the woman attempted to teach language to the dolphin. Peter was reportedly a demanding 'roommate', and the woman eventually withdrew from the project. While a basic communication did develop, reportedly similar to that between a dog and a human, deeper exchanges - of dolphin whistles or human words - did not occur.
Lilly's work ended in the 1980s. Since then, researchers led by Louis M. Herman have developed a new approach to communication studies with captive bottlenose dolphins at the University of Hawaii. Their goals have been to discover how dolphins process information - both through sight and sound, how they learn, and how they communicate. Herman's research has verified earlier findings that dolphins have good memories and can mimic a wide variety of sounds. Able to store new information, they can also quickly update old information.
The dolphin's most impressive accomplishment is its ability to understand sentences expressed in either an artificial acoustic or a visual language. In the experiments, the "words" of the language are sounds generated by a computer and broadcast via an underwater speaker. First the dolphin learns words such as fetch, ball and hoop. The words refer to (1) objects in the tank; (2) actions that might be taken in connection with the objects; and (3) modifiers of place or location. In "sentences" of two or more words, the dolphin is then told to do something. The level of understanding is measured by the accuracy and reliability with which the dolphin carries out the instruction.
Dolphins perform very well on such tests. To more than 600 two-word sentence instructions, the dolphins gave correct responses about 80 percent of the time. They also understood "new" instructions almost as well as familiar ones, with only a slight advantage to the familiar. New instructions consisted of fresh combinations of words that either obeyed the language rules or, in a few cases, were logical extensions of existing rules.
These and other experiments clearly show that dolphins can learn rules and understand certain abstract concepts. They can also work with both auditory and visual symbols. Compared to apes which have been taught to use America sign language - an exclusively visual medium for communication - the dolphins have more range. The apes, on the other hand, learn more quickly in tests involving symbols. Of course, all of these are laboratory feats and prove nothing about life in the wild - for dolphins or apes.
In the future, trained dolphins may be able to grasp more complex human-taught vocabularies. But this does not necessarily mean that dolphins have their own language. No-one yet knows where this research will lead, but many scientists feel that we have only glimpst what really goes on inside the mind of a wild dolphin.
Can dolphins kill sharks?
Dolphins and many shark species are similar in shape and size, and inhabit the same regions and depths of the ocean. Sharks have a reputation for being fierce predators. hardly surprising when they are armed with rows of sharp serrated teeth that can easily bite through flesh and bone. Unlike dolphins, sharks have a very tough, sandpaper-like skin that is not easily punctured.
Dolphins, on the other hand, are seen as intelligent, playful creatures. They only have a single row of peg-like teeth which is mainly used for catching smaller fish. Their skin is soft, flexible and can be cut easily.
Since dolphins normally travel together in a group - known as a pod, if one of them is threatened by a shark, the other members of the group will join in to defend the dolphin that is in danger.
The dolphin's main weapon is their snout, otherwise known as their beak. It is made of very strong and thick bone, and has a hard, rounded end.
However, attacking dangerous sharks clearly has an element of serious risk and so dolphins are often unwilling to attack the 'bigger boys' such as white sharks, tiger sharks, mako sharks and bull sharks, unless of course they have good reason to ie. protecting pregnant females, calves or injured individuals.
However, if a pod has no good reason to stay and fight then they will, more often than not, swim away.
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Based on articles by Wildlife Fact-file and http://www.dolphins-world.com/what_do_dolphins_eat.html and http://en.wikipedia.org/wiki/Dolphin and http://www.10interestingfacts.com/dolphin-facts
Based on an article from http://en.wikipedia.org/wiki/Dolphin and http://www.harmlesslion.com/dolphins/ah_comm.htm
Photos care of http://voltaicsystems.com/blog/solar-bags-used-for-dolphin-research/ and http://www.2dolphins.com/category/dolphins/ and http://www.treehugger.com/natural-sciences/new-discoveries-in-dolphin-communication-reveal-use-of-diplomacy-to-avoid-fights.html and http://www.globalanimal.org/2011/09/11/dolphins-dont-just-squeak-they-speak/50761/
Photo care of http://www.huntercourse.com/blog/2011/06/natures-most-skilled-hunters/ and http://www.10interestingfacts.com/dolphin-facts