Bottlenose Dolphins



Dolphins are mammals that are excellent swimmers. They are predators of great skill. I have liked dolphins (especially the bottlenose dolphin, or in biological name: tursiops truncatus) since I was about 5 years old.



                                           Identifying Bottlenose Dolphins

Bottlenose dolphins are 8-12 feet, or 2.4-3.7 meters long. Their color can be different on the back: shades of gray, such as gray-brown, gray-green, or even plain gray; while on the belly part and below the jaw, it is white. Bottlenose dolphins have 18-26 small, sharp predator teeth on both the upper and lower jaws. Also, bottlenose dolphins really do have bottle-shaped noses, for that’s what gave them their name.



                            Bottlenose Dolphin Population, Birth, Herds, and Types

The bottlenose dolphins’ population is quite large, so they are not close to being endangered. And this is partially because bottlenose dolphins adapt well. I say this because even though bottlenose dolphins have been taken from their habitats to another place (e.g. aquariums), they have a lifespan about the same as the wild-bred dolphins. Bottlenose dolphins use behavioral signs to show that they are willing to mate. The newborn calf is approximately 3-4 feet. Calves are born 12 months after they first appear in their mother’s belly. A mother bottlenose dolphin will nurse its calf for more than one year (the calf’s actual time with its mother is about 3-6 years). Sometimes another bottlenose dolphin will stay close to the mother and calf to help. This helper dolphin is called an “auntie” dolphin, and is usually the only other bottlenose dolphin that the mother will let close to her calf. A normal, female dolphin will usually give birth to a calf every 2-4 years. Bottlenose dolphins live in herds, called pods, with 10-25 bottlenose dolphins, but they have been known to often make a giant group with hundreds of bottlenose dolphins in it. Dolphins are very social animals. They can make sounds that scientists believe, but are not able to prove, to be a type of language. There seems to be two types of bottlenose dolphins, the coastal one and the offshore one. They both vary in their body shape and diet (the different diet will be shown later).



                                           How Bottlenose Dolphins Swim

Bottlenose dolphins swim by moving their tail flukes up and down through the water. They use their pectoral flippers to steer while swimming, to stroke, or to touch each other. Bottlenose dolphin “friends” or closely bonded dolphins may swim turning or twisting, or face to face touching flippers. The fastest a dolphin has swum was 7.3 meters per second (this dolphin was being chased by a speedboat), while the record for depth is over 1,640 feet (500 meters), and the record for the highest jump is 20 feet (6 meters).   



                                           How Bottlenose Dolphins’ Sonar Work

Bottlenose dolphins (and other toothed whales) can produce high pitched clicks. When these clicks hit an object, some of the sound will come back. By listening to the echo and interpreting the time it took for the echo to come back, dolphins can estimate how far an object is from itself (that’s why sonar is also called echolocation: by listening to the echoes, a bottlenose dolphin can guess the location of the object). Depending what the object is, the sound may penetrate into the object and bounce off the inner structure. If the object is a fish, some of the body parts may bounce back (e.g. the skin on the dolphin’s side, some of the bones, the internal organs, and the skin on the other side) and create some weaker echoes. The echoes will give the dolphin information about the structure and size of the fish. By moving its head, it will get more information about the fish. Dolphins can also combine their sonar with their vision.



                            How and What Bottlenose Dolphins Eat, Drink, and Breathe

Coastal bottlenose dolphins eat a wide variety of fish (e.g. mullet, mackerel, herring, and cod) and squid, while offshore bottlenose dolphins prefer squid. Bottlenose dolphins don’t use their teeth to chew their food; they use them to grip their food, and then swallow it whole. Bottlenose dolphins swallow their food head first, so the spines of the fish don’t get caught in their throats. Bottlenose dolphins cooperate in hunting and have been reported to herd fish into groups, and then taking turns to feed in the schools while others keep guard, or trapping schools of fish against sand banks for an easy dinner. Bottlenose dolphins don’t get water from the oceans because they would drink more water to get rid of the salt in the salty ocean water than they would have drunk in the first place. Most of the water a bottlenose dolphin gets comes from its food (fish and squid). Also, when they burn their fat, water gets released in the process. Their kidneys are also adapted to keeping the maximum amount of water possible. Even though they live in water, they have life like desert animals, since they have no direct source of fresh, drinkable water. Bottlenose dolphins breathe by a blowhole located on the top of their head. They need to breathe about every two minutes, but can hold their breath a bit longer. The air leaves the blowhole at 100 miles per hour. Complex nerve endings around the blowhole sense pressure changes so the dolphin knows exactly when the blowhole is in or nearing the air and can be opened. Water in a dolphin's blowhole will actually drown it so powerful muscles close the blowhole as it dives under the water again.



                            How Old Bottlenose Dolphins Can Get, and How They Die

Bottlenose dolphins have a big range for their lifespan. If you put them together, bottlenose dolphins have a lifespan of 10.3-50 years. But dolphins have another reason to die: predators killing them. Some sharks (including tiger sharks, dusky sharks and bull sharks) and orcas (killer whales) will prey upon dolphins. Dolphins (and whales) are also often trapped in people’s fishing nets.





                            Why I Chose the Subject of Bottlenose Dolphin

I chose to write about bottlenose dolphins because I think they are cute. I really like dolphins, so I thought it would be a good time to learn about them while typing an essay.



                                           The Resources I Used

I used four websites for my research, and I thought they were all great.

1st: NOAA's Bottlenose Dolphin page

2nd:'s Dolphin Info page

3rd:'s Dolphins page

4th:'s Bottlenose Dolphin page

If you want info, I suggest the first, second, and fourth. The third one mostly shows pictures.