Dolphin<<<< Back to marine animals
- Kingdom: Animalia
- Phylum: Chordata
- Class: Mammalia
- Order: Cetartiodactyla
- Suborder: Whippomorpha
- InfraOrder: Cetacea
- Family: Delphinidae
- Conservation status: Least concern
- Areal: All Oceans
- Habitat: All Oceans
- Food: carnivore
- Length: 1.7 - 9.5m (5.6 - 31 ft)
- Weight: 50kg - 350 kg
- Lifespan: 20 - 30 years
- Reproduction: 1 - 2 calfs
Dolphins are marine mammals closely related to whales and porpoises. There are about 40 dolphin species and 17 genera. They very in size from 1.2 m and 40kg to 9-10m and 10 tons. We can see them all over the world, especially in large shallow continental areas. The Delphinidae family is the largest order of cetaceans; dolphins have evolved 10 million years ago. Dolphins are the most intelligent animals and often their friendly appearance and playful attitude have made them really popular.
Their name originates from the Greek word delphus which means "fish with navel".
Dolphins are carnivore mammals, with special adaptations for their predatory feeding type. By analyzing the stomach contents, dolphins consume on average 8-20 kg of fish daily. There are various methods of feeding dolphins. Fish and squid are their main food. The group of dolphins will surround the fish in shallow waters to make it easier to catch. In general, the Black Sea dolphins feed on fish and focus on fish schools (flounder, sole, anchovies, sprats, mackerel). Therefore the hunt needs to be done in group, and the success depends on a good coordination and communication.
In terms of sense of taste, anatomical studies showed that on the tip and sides of the tongue there are special formations, that receive taste excitations (taste buds). The dolphins have the ability to perceive the difference in taste from sweet to salty, sour and acid.
Dolphins have a fusiform body, adapted to fast swimming. The tail fin, called „fluke” is used for propulsion, while the pectoral fins together with the tail give him the directional control. Their dorsal fin provides stability while swimming. Although it varies depending on the species, the base color is gray with various shades, often with many different lines and spots of color in contrast. The head contains the so-called biological sonar device (used by submarines, met only at few animals).
Many species have their jaws looking like an elongated distinct beak. For example bottlenose species has a curved mouth that shows a fixed smile. Some species have up to 250 teeth. Dolphins breathe through a hole situated on the top of their head. Their brain is large and complex and its structure differs from that of many animals. Unlike most animals dolphins have no hair, except a few loose threads, that they lose shortly after birth. Males have two slits in the lower body part hiding the penis and anus. Females have only one that covers both the anus and vagina.
Most species of dolphins have an exceptional view, they can see both in water and on land well. They can also hear frequencies ten times higher than people can. It is believed that their ears are connected to the jaw and the biological sonar; in water the sound is led to the middle ear. It is believed that its teeth are used as an antenna that captures reception sounds for the exact location of an object.
The sense of touch is also well developed. Nerve endings are found on skin, especially around the muzzle, pectorals and genitals. With all these enviable qualities it is believed that the dolphins lack the sense of smell.
Dolphins are considered the most intelligent animals on Earth, hard to say just how intelligent. Dolphins behaviour has been studied intensively both in captivity and in the wild. They are social animals that usually live in groups of 10-15 individuals. In areas rich in food the groups join together forming a large group.
They communicate through various whistles, snapping, trilling and other vocalizations. They can establish strong social bonds, staying close to the ill or wounded ones and helping them breathe by pushing them to the surface. Often protect people by chasing sharks away.
Dolphins, like humans engage in disputes on various themes: disputes between companions, competition for females, etc. Because of this on the dolphins adult bodies scars can be seen. In the Black Sea we encounter three species: common porpoise, bottlenosed dolphin and common dolphin. Around 2300 specimens were monitored in the Black Sea.
Copulation happens face to face, the bellies are touching the entire time and they engage in long preludes. Usually intercourse is short and can be repeated several times in a short period of time. The gestation period varies according to the species and is approximately 11-12 months. For the orca is approximately 17 months.
The orca is the largest species of dolphin. Usually dolphins become sexually active at a young age, even before reaching adulthood. The age of sexual maturity varies by species and sex. Dolphins are known to have sex for other reasons besides reproduction. Various species sometimes engage in intercourse with other species and in some cases the partners will become violent.
What is very unique about the birth of a dolphin calf is that it is born tail first instead of head first like all other mammals. The females will move to very shallow water for the young to be born. They are often accompanied by one or two other dolphins that will assist with the birth. Usually, those assistants are females but they can also be male.
The assistance is very similar to the birth of a human baby. The other dolphins soothe the mother and they help with the calf when it is born. They aid the calf to the surface of the water to get its first breath. These young are coordinated to swim, they have their eyes open, and their senses are fully alert.
The average lifespan is 20 to 30 years.
Did you know that:
A study showed that dolphins are the only animals besides people that develop a natural form of type 2 diabetes?
The dolphins nose opens through a single nostril situated in a small dent on the head, called blowhole.
Under the skin there is a layer of fat that can reach 30 cm.
The dolphin is an aquatic mammal able to emit and receive sound signals simultaneously on multiple channels.
Dolphins don’t have vocal cords.
The eyes are protected against salt water by a tear membrane.
Top speed for a bottlenose is around 32 km/h, but the common dolphin can swim with a speed of 60 km/h.
Dolphins use their teeth to grab and not to chew.
Often, in the dolphins body, after dissection, remains of lower limbs are found, proving that they were once land mammals.