Dolphins are highly intelligent marine mammals.
Dolphins have smooth skin, flippers, and a dorsal fin. They have a long, slender snout with about 100 teeth, and a streamlined body.
This aquatic mammal has been able to fascinate us in a variety of ways.
They are curious, form strong bonds within their pod, and they have been known to help humans in a variety of circumstances including rescues and with fishing.
There are 43 different species of dolphins that have been recognized. 38 of them are marine dolphins which are those that we are the most aware of and 5 of them are river dolphins.
The largest and heaviest is the orca, or killer whale. They are from 7 to 9.7 meters (23 to 32 feet) long and weight up to 7.5 tonnes ( 8.3 short tons).
Hector’s dolphin is the smallest of the dolphins. Mature adults have a total length from 1.2 to 1.6 meters (3-ft-11-in to 5-ft-3-in) and weigh from 40 to 60 kilograms (88 to 132 pounds).
Lifespan is from 20 to 90 years, depending on species.
Most species live in shallow areas of tropical and temperate oceans throughout the world.
Dolphins are highly social animals, often living in pods of up to a dozen individuals, though pod sizes and structures vary greatly between species and locations. In places with a high abundance of food, pods can merge temporarily, forming a superpod; such groupings may exceed 1,000 dolphins.
They have to come to the surface to for water at different intervals to get air. This can be from 20 seconds to 30 minutes between when they get air.
The single blowhole on top of their head has a flap that opens to reveal a pair of nostrils, which dolphins use for breathing when they surface.
Dolphins have to be conscious to breath. This means that they cannot go into a full deep sleep, because then they would suffocate. Dolphins have “solved” that by letting one half of their brain sleep at a time. This has been determined by doing EEG studies on dolphins.
Dolphins have an eye on each side of their head. Each eye moves independently of the other, so dolphins can see ahead, to the side, and behind them. They can also see very well both underwater and above water. Their vision out of the water is about as good as a cat’s or a dog’s vision.
Their ear holes are tiny, about the size of a crayon point, but dolphins probably have the best hearing in the Animal Kingdom. They receive sounds through their jawbone and head, and the vibrations pass into the tiny bones of their inner ear.
All dolphins make sounds that travel underwater, bounce off something, and then return to the dolphins as echoes. This sophisticated echolocation allows dolphins to find food or avoid predators, even in dark or murky water.
While some dolphins eat fish like herring, cod or mackerel, some others eat squids. Even more, large dolphins like the killer whales, eat some other marine mammals like seals or sea lions and sometime even turtles.
On average an adult dolphin will eat 4 to 9% of its body weight in fish, so a 250 kilograms (550 pounds) dolphin will eat 10 to 22.5 kilograms (22 to 50 pounds) fish per day.
They usually work as a team in their pod to get the school of fish surrounded and balled up. From there, they can plow through the middle and eat plenty as they do so.
Dolphins also work together to help when one animal is sick, hurt, or giving birth. They take turns pushing the hurt or young dolphin to the surface so it can breathe. Pods of dolphins will attack an intruder as a group and can even kill a large shark by ramming it as a group!
Many types of animals have strict annual breeding seasons, but that isn’t so for dolphins. While they often can reproduce at any time, dolphins in certain geographic locations partake in heightened mating activities during both the spring and autumn seasons.
For dolphins the average gestation period can vary significantly depending on the species from 9 months all the way up to 17 months.
Dolphins give birth to live calves while staying in relatively shallow waters.
With twins being a very rare occurrence, dolphins usually give birth to one calf. As soon as the calf is brought into the world, the mother must quickly take it to the surface for its first breath and will nurse the calf with her own milk for at least 12 months.
Most dolphin calves will stay with their mothers for 3 to 6 years.
For most of the smaller species of dolphins, only a few of the larger sharks, such as the bull shark, dusky shark, tiger shark and great white shark, are a potential risk, especially for calves. Some cases of killer whales eating dolphins have been documented, but is not a common behavior.
Although some dolphin species are considered an endangered species, alarming statistics suggest that more and more dolphins are being killed by illegal dynamite fishing, being caught in fishing nets, collisions with boats and or propellers, marine pollution, disease and beaching due to sonar interference than ever before.
Dolphins are, in fact, not monogamous.
Dolphins have several highly developed forms of communication. They have a “signature whistle” which allows other individuals to recognise them.
Dolphins are able to hear a broader range of frequencies than humans. While we can hear sounds from 20 Hz to 20 Khz, dolphins are able to hear from 20 to 150 Khz being up to 7 times more sensitive than human ear.
Some dolphins can jump as high as 9 meters (30 feet) above the water’s surface.
Dolphins don’t drink sea water. They get the water they need from the fish they eat.