The Wonderful World of Dolphins
By: Tamara Thomason
Introduction
As you read this book, click on the coaches down on the bottom. They will ask you questions or tell you more about what you just read. Some pages also have a Response Area, where there is a question and a place for you to type in your answers.
There are 43 different dolphin species . Thirty-eight of these species are oceanic dolphins and five are river dolphins. Dolphins are not fish; they are actually mammals like us. This means that they are warm-blooded, give birth to live young, and nurse their young. Because they are mammals, they cannot breathe under water and have to go to the surface two or three times a minute to breathe. Dolphins travel in pods containing anywhere between five to several hundred dolphins.
Bottlenose Dolphins
Bottlenose dolphins are the species that most people are familiar with. They are the most likely of the dolphin species to approach humans out in the wild. They are well-known and loved because it looks like they are always smiling. Their faces curve upward on the sides, giving this impression.
The majority of bottlenose dolphins live along the coast of the USA. They can be found from Cape Cod all the way down to the Gulf of Mexico.
Habitats
Most dolphins live in salt water (the ocean), but the five species of river dolphins can live in freshwater. Dolphins tend to live in tropical areas and along coasts. They live in shallow areas because they need to come up often in order to breathe.
Hunting and Food
In order to find food, dolphins use echolocation . Echolocation is when a dolphin sends out sound waves that bounce off of objects, providing a sort of picture. This picture tells the dolphin the location of something, how big it is, and the direction it is moving. Echolocation can also help dolphins communicate with each other.
Dolphins do not often hunt for food alone. They usually hunt with their pod . The pod will swim in a circle around a school of fish, herding them into a tight little ball. The dolphins will then take turns swimming through the ball and feeding on the fish.
They mostly eat fish, but they also eat crustaceans and squid. They can consume between 10 and 35 pounds daily.
Communication
Dolphins communicate through clicks and whistles. When underwater, they use echolocation to communicate with other dolphins. Dolphins all have their own unique whistle- like you have your own name. This helps to tell dolphins apart.
Appearance
Most dolphin's are generally gray with their backs being a darker shade of gray. Their skin is smooth and feels like rubber. Their eyes are on the sides of their heads.
A dolphin's appearance does vary from species to species though. For example, the striped dolphin has blue and white stripes on its body. The shape of a dolphin's dorsal fin also changes based on the species of dolphin. Snouts can also be different.
Playtime
Dolphins are very social and love to play. They play with each other, other ocean animals, and humans. They will splash water at each other and dance. They will use about anything as a toy, even seaweed!
Dolphins to the Rescue
Dolphins have been seen helping injured or sick dolphins to the surface of the water so that they can breathe. There have also been many reports of dolphins helping rescue humans from sharks. They have guarded humans from sharks until they could be saved. Dolphins have also been reported to help people to shore when they are stuck in water.
What threats do dolphins face?
Commercial fishing threatens dolphins in that they become tangled in the nets and other fishing equipment.
Another threat dolphins face is programs such as therapy, swimming with the dolphins, and parks like Sea World. Because of these programs and parks, more and more dolphins are being held in captivity.
Global warming is also threatening in that it has caused a reduction in their food supply.
Migration
Dolphins migrate only to follow the food supply or to move to waters with temperatures that better suit them. If they have what they need where they are, they will not migrate.
Fun Facts
Killer whales are actually a type of dolphin. They are the largest dolphin species. They are called killer whales because they kill whales, not because they are whales.
Dolphins sleep by resting half of their brain at a time. This is so that the dolphin can keep going up for air and not drown. It also allows them to keep one eye open to look for predators .
Dolphins can be pregnant for a year. After birth, dolphins nurse for about 19 months and stay with their mothers for three to five years before going off on their own. The females are called cows, the males are called bulls, and the babies are called calves.
Most dolphins have long lives. Bottlenose dolphins can live over 40 years. Females usually live about 50 years. Killer whales can live for over 70 years.
Dolphins have about 100 teeth, but only use them to grab prey. They don't chew their food, but swallow it whole.
Dolphins have two stomachs like cows. The first one stores food and the second one is where digestion takes place.
Dolphins teach their young how to use tools such as sponges on their snouts to protect them while searching for food. Not many mammals besides humans are known for using tools. Dolphins are highly intelligent.
A large sized dolphin can be 14 feet long and weigh up to 1100 pounds. Dolphins who live in cooler water are often larger than dolphins living in warmer waters.
They can jump up to 20 feet in the air and dive up to 1000 feet.
Extensions
To find out more about dolphins, click on this link!
http://kids.nationalgeographic.com/animals/bottlenose-dolphin/
Unscramble these vocabulary words.
pindloh
odp
eryp
cispsee
Talk Like A Scientist
Use the word echolocation to discuss how dolphins communicate.
Fill in the blanks:
A _________is a group of dolphins.
Something that comes from the ocean is called ___________.
An animal that hunts and eats other animals is called a __________.
Word bank: Pod, Oceanic, Predator