Dolphins are arguably one of the most interesting creatures on this planet. They are considered mammals despite their aquatic inhabitation, much like whales and porpoises. Dolphins give birth to live young usually after a long gestation period that varies between 11 months to 17 months among the different species. To be considered a mammal, an animal must have some form of body hair, dolphins are no exception. A baby dolphin, called a calf, is born with whiskers on its upper jaw, but these fall out after birth.
These aquatic mammals are one of the most cunning and adaptable out there. Dolphins have even been observed chewing on the highly poisonous puffer fish to get high.
Dolphins are also very adept swimmers, with some species being able to move around at speeds of up to 34.5 mph.
They are one of the few animals in the world that use echolocation to locate objects around them. Also very social in nature, dolphins are often seen in groups, called pods, of up to 30 individuals.
Like most marine creatures, their coloration helps them to stay camouflaged. When seen from above the surface of the water, their greyish-blue skin blends in with the sea floor below, but when seen from underneath, their lighter bellies makes them blend in with the sky.
Types of Dolphins
Dolphins are divided into several species. Some of the more common are bottlenose dolphins, river dolphins, spotted dolphins, and Pacific white-sided dolphins. Some species, known as blackfish, are considered to be whales – these are the killer whale, pygmy killer whale, melon-headed whale, false killer whale, and both subspecies of the pilot whale.
More often than not, the word dolphin is used to refer to the three species of this genus, which are, the common bottlenose dolphin, the Indo-Pacific bottlenose dolphin and the Burrunan dolphin.
The Burrunan variety was given species recognition in 2011. Bottlenose dolphins inhabit all oceans except the Arctic and Antarctic. Tuffy, a US Navy trained bottlenose, dove to a depth of 990 ft, which is the deepest dolphin dive recorded.
River dolphins stay exclusively in brackish water or freshwater. There are many families included under this bracket, like the Ganges river dolphins, Amazon river dolphins, Bolivian river dolphin, and La Plata dolphin, among others. River dolphins vary in size from the mere 5 ft South Asian river dolphin to the 8 ft long Amazon river dolphin. Their closest extant relative is the hippopotamus, with the two believed to have separated around 40 million years ago.
New Species of Dolphins
In addition to the newly discovered Burrunan dolphin, another species has also been found off the northern coast of Australia and Southern New Guinea, known as the Australian humpback dolphin. It was given a scientific description in 2014, thus becoming the fourth humpback species to be recognized. The actual population size of this species is still a mystery, but estimates suggest at least a few thousand individuals. The Australian humpback dolphin is different from the other humpbacks in length, vertebrae, number of teeth, and range of distribution.
Feeding habits of dolphins vary between species, depending on size and prey availability. While squid and fish are common favorites, larger dolphins, like the false killer whale and orca, routinely prey on other aquatic mammals. There are two techniques used for catching their food; herding and corralling. When dolphins herd, members of a pod manipulate a school of fish into a small area, and then take turns to plow their way through the collection of the stunned fish. When corralling, dolphins chase their prey into shallow water to make the task of catching them easier.
There are several examples of dolphins being able to strategize profitable ideas for themselves. A captive dolphin in a US research center, Kelly, who had been trained to keep her tank clean, figured out a way to manipulate her trainers to give her more food.
Kelly figured out that she received the same fish regardless of the size of the piece of trash she was delivering to her trainer. So she began hiding big pieces of trash under a rock. Kelly would then rip off small pieces from the trash and deliver them one at a time so that she could receive more fish. – Source
Dolphins can also use tools to their advantage. They are often trained by the military, especially in the navies, where they are used to locate underwater mines and depth charges, as well as look for missing persons. The Soviet Navy had a program where they researched the effectiveness of marine mammals in the military, but it was shut down in the early 1990s.
Considering their special place in the world, dolphins need to be protected at all cost. Despite their large range of distribution, there are certain species that are threatened with extinction, and some have already gone extinct. There are efforts underway to ensure the safety of this marvelous animal for posterity.