Bottlenose Dolphin

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Bottlenose Dolphin

For several reasons, bottlenose dolphins are the cetaceans that the majority of people are most familiar with. They are not the most common dolphins – that title belongs to the aptly named Common Dolphin – but they are one of the most frequently seen since they tend to remain closer to shore than many other species. But, even if a person has never seen a live dolphin, there is a very good chance that they have been exposed to one of the many cultural references, from movies, art, jewelry, and the well-received TV show ‘Flipper’.

Content List

1. Scientific & Common Names

2. Characteristics

a. Breeding

b. Behavior

3. History

4. Present Status

5. References


Scientific & Common Names

Kingdom - Animalia

Phylum - Chordata

Class - Mammalia

Order - Cetacea

Suborder - Odontoceti

Family –Delphinidae

Genus – Tursiops

Species- Tursiops truncates (common bottlenose) and Tursiops aduncus (Indo-Pacific bottlenose)

Common names: bottlenose dolphin


Characteristics

Named for their rounded and stubby beak, the bottlenose is a large dolphin and can reach sizes of 8-12 feet and very large individuals can weigh as much as 1400 pounds. They can live from 40-50 years but the age they reach maturity depends on the area they are found and ranges from 5-14 years. Although there can be slight variations in their shading, they tend to be light to medium grey above, fading to a light or even pinkish grey on their bellies. Unique in oceanic dolphins, but similar to belugas, bottlenose have much more movement in their necks since not all of the vertebra in their necks are fused.


Breeding

Dolphins have strong family ties and this is very evident in the relationship between a mother and her calf. Mating can occur year round but there are peaks in births during the spring and autumn. Gestation lasts twelve months. Since they are mammals, the calves will nurse from their mothers and this lasts for a year to a year and a half. Even after nursing has stopped, the mother and calf remain together for many years as the calf learns hunting techniques and the complex language of clicks and whistles the dolphins use.


Behavior

Bottlenose dolphins can be found worldwide in warmer waters and even venture into lagoons and rivers. They do not stray beyond the brackish waters in rivers since they are a marine species, but there are several other species of dolphin that are solely freshwater. They will hunt individually or cooperatively and there is evidence that they will hunt jointly with bluefin tuna. They are social and talkative, using sounds and body movement to communicate. They can be dangerous to humans but are often helpful, even endangering themselves to support swimmers in danger from sharks. The reason for their seeming desire to connect with humans has been used as an indication of their higher intelligence, but there is no way of knowing their motivation.


History

The history of dolphins is a complicated one. Although life originated in the ocean, whales and dolphins evolved from land animals that returned to the sea sixty-five million years ago after a asteroid impact on the Yucatan Peninsula rendered life on land difficult. Although the exact animal that they descended from is still being studied and debated, it is widely believed that their common ancestor was a carnivorous hoofed animal similar to an antelope. The remains of their landed history can be seen in the structure of their spine and the bones in their fins that resemble the appendages of land based mammals. If the hoofed ancestor theory is correct, that leads to an interesting implication that the immediate ancestors of modern day hoofed herbivores were once carnivores.


Present status

Dolphins have traditionally been seen as a nuisance and they were hunted by fishermen who viewed them as an impediment to their trade. Today, dolphins are not hunted as widely as they once were and there are many protections in place, but there is still pressure on their populations from marine debris, pollution, and from those few countries who still consume them. While bottlenose dolphins are not considered currently at risk, other dolphins are not so fortunate. Hector’s and Maui’s dolphins, found near New Zealand, are seriously endangered and the Chinese river dolphin (lipotes vexillifer), also known as the baiji was declared functionally extinct when none were found during a survey of their territory in 2006.


References

No Turning Back: The Life and Death of Animal Species by Richard Ellis

Wild Animals of North America from National Geographic Society

Men and Whales by Richard Ellis

The Bottlenose Dolphin: Biology and Conservation by John E. Reynolds, Samantha D. Eide, and Randall S. Wells

Dolphin Societies: Discoveries and Puzzles by Karen Pryor , Kenneth S. Norris

Dolphin Confidential: Confessions of a Field Biologist by Maddalena Bearzi