Dolphin

**Dolphins** are part of the toothed whales. Generally, they are among the smaller whales. Most live in salt water oceans, but there are also river dolphins. They are mammals, not fish.  

Dolphins are usually between  and  long. The largest dolphin, the orca (killer whale), can be up to  long. 

## Name 
The dolphin was first thought to be a fish with a womb. For this reason, it was named "dolphin," which comes from the Ancient Greek word δελφίς (*delphis*), meaning "with a womb". Today, though, dolphins are known to be highly intelligent mammals, not fish. Dolphins have fought off sharks by ramming them over and over again with their snouts and heads. 

Sharks look after the young when the mothers need to leave their calves to hunt for food. The young need to breathe more often than the adults, and the food may be in deeper waters.

Dolphins "porpoise" in and out of the water when traveling at high speed. Scientists do not know for sure why they do this. It may be the fastest movement they are capable of. 

### Diet 
Dolphins are carnivores and eat fish. They use echolocation to find their food.

When they chase fish, the fish go into a "bait ball" to self-protect. In turn, the dolphins attack in a group and eat as many fish as they can.

## Habitat 
Oceanic dolphins are marine animals living in the sea. They live in all of the oceans.

Three of the four species of river dolphins live in fresh water rivers. The La Plata dolphin lives in saltwater estuaries and the ocean. Water pollution and the loss of habitat are a threat to some dolphins, especially those living in rivers and estuaries.
## Sleep 
Dolphins (and other cetaceans) sleep in the water. There is danger from animals that eat dolphins. To guard against danger from animals that eat dolphins, they have two sides of their brain. One side sleeps, while the other side stays awake.  

Dolphins do things while asleep: 

* Dolphins will keep one eye open to watch for animals that eat them while they sleep. 
* Dolphins also swim in circles when they are sleeping to look around for danger.
* Dolphins get their nose out of the water to breathe. 

Dolphin groups or species have their own way of sleeping. Pinnipeds, like seals, can sleep like dolphins. The Ancient Greeks welcomed dolphins; spotting dolphins riding in a ship’s wake was considered a good omen. 

In Hindu mythology, the Ganges River Dolphin is associated with Ganga, the deity of the Ganges River.

### Cuisine 
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Dolphin meat is eaten in a few countries, including Japan and Peru (where it is referred to as *chancho marino*, or "sea pork"). Japan may be the best-known and most controversial example, but worldwide, eating dolphin is not common.

### Dolphin therapy 
Dolphin therapy is sometimes used for people with mental or physical disabilities. It involves contact with trained dolphins. 

Scientists do not agreed on whether dolphin therapy is any better than the usual treatments. Scientists continue to study this treatment method.

## Taxonomy 
### Oceanic dolphins (*Delphinidae*) 
*Some examples:*
* Genus *Delphinus*
** Common Dolphin (*Delphinus delphis*)
* Genus *Tursiops*
** Bottlenose Dolphin (*Tursiops truncatus*)
* Genus *Orcinus*
** Orca (*Orcinus orca*)
* Genus *Feresa* 
** Pygmy killer whale *Feresa attenuata*
* Genus *Pseudorca*
**False killer whale *Pseudorca crassidens*
* Genus *Globicephala*
**Long-finned pilot whale *Globicephala melas*
**Short-finned pilot whale *Globicephala macrorhynchus*
* Genus *Peponocephala*
** Melon-headed whale *Peponocephala electra*

### River dolphins 
* Amazon river dolphin or Boto (*Inia geoffrensis*)
* Chinese river dolphin or Baiji (*Lipotes vexillifer*) (likely to be extinct)
* La Plata dolphin (*Pontoporia blainvillei*)
* South Asian river dolphin *Platanista gangetica*
** Indus river dolphin (*Platanista gangetica minor*)
** Ganges river dolphin (*Platanista gangetica gangetica*)

## Gallery 

File:Dolphin Anatomy.svg|Anatomy of a dolphin, including its skeleton and internal organs
File:Killer Whales Hunting a Seal.jpg|Orcas (*Orcinus orca*) hunting a seal
File:Ichthyosaur vs dolphin.svg|Dolphins display convergent evolution with fish and aquatic reptiles such as ichthyosaurs.
File:Baiji 1.jpg|The baiji, a functionally extinct species of river dolphin
File:Dead dolphin, close-up - geograph.org.uk - 2419159.jpg|A dead dolphin
File:Bottlenose dolphin, Azores (51841112505).png|Bottlenose dolphin (*Tursiops truncatus*)
File:NMMP dolphin with locator.jpeg|KDog, a common bottlenose dolphin of the United States Navy Marine Mammal Program. Here he is shown wearing a locating pinger in the Persian Gulf.
File:Hourglas dolphin.jpg|Hourglass dolphins (*Lagenorhynchus cruciger*) leaping in the Drake Passage

## References
## Other websites 
* https://www.fisheries.noaa.gov/species/common-bottlenose-dolphin
* https://uk.whales.org/whales-dolphins/facts-about-dolphins/