9781422276716

T h e A m a z i n g Wo r l d o f S h a r k s

BLUE SH RKS

T h e A m a z i n g Wo r l d o f S h a r k s

BLUE SHARKS BULL SHARKS

DEEPWATER SHARKS FRESHWATER SHARKS GREAT WHITE SHARKS HAMMERHEAD SHARKS MAKO SHARKS RAYS THRESHER SHARKS TIGER SHARKS

T h e A m a z i n g Wo r l d o f S h a r k s

BLUE SH RKS

By Elizabeth Roseborough

MASON CREST

Mason Crest 450 Parkway Drive, Suite D Broomall, Pennsylvania 19008 (866) MCP-BOOK (toll-free) www.masoncrest.com

Copyright © 2019 by Mason Crest, an imprint of National Highlights, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, taping or any information storage and retrieval system, without permission from the publisher. First printing 9 8 7 6 5 4 3 2 1 Printed in the USA ISBN (hardback) 978-1-4222-4122-6 Names: Roseborough, Elizabeth, author. Title: Blue sharks / Elizabeth Roseborough. Description: Broomall, Pennsylvania: Mason Crest, [2019] | Series: The amazing world of sharks blue sharks | Includes bibliographical references and index. Identifiers: LCCN 2018013883 (print) | LCCN 2018019033 (ebook) | ISBN 9781422276716 (eBook) | ISBN 9781422241226 (hardback) | ISBN 9781422241219 (series) Subjects: LCSH: Blue shark--Juvenile literature. Classification: LCC QL638.95.C3 (ebook) | LCC QL638.95.C3 R67 2019 (print) | DDC 597.3/4--dc23 LC record available at https://lccn.loc.gov/2018013883 Developed and Produced by National Highlights Inc. Editor: Keri De Deo Interior and cover design: Priceless Digital Media Production: Michelle Luke QR CODES AND LINKS TO THIRD-PARTY CONTENT You may gain access to certain third-party content (“Third-Party Sites”) by scanning and using the QR Codes that appear in this publication (the “QR Codes”). We do not operate or control in any respect any information, products, or services on such Third-Party Sites linked to by us via the QR Codes included in this publication, and we assume no responsibility for any materials you may access using the QR Codes. Your use of the QR Codes may be subject to terms, limitations, or restrictions set forth in the applicable terms of use or otherwise established by the owners of the Third-Party Sites. Our linking to such Third-Party Sites via the QR Codes does not imply an endorsement or sponsorship of such Third-Party Sites or the information, products, or services offered on or through the Third-Party Sites, nor does it imply an endorsement or sponsorship of this publication by the owners of such Third-Party Sites. ISBN (series) 978-1-4222-4121-9 ISBN (ebook) 978-1-4222-7671-6 Library of Congress Cataloging-in-Publication Data

CONTENTS

FUN FACTS

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CHAPTER 1 - INTRODUCING BLUE SHARKS

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CHAPTER 2 - THE BLUE SHARK’S POPULATION AND HABITAT

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CHAPTER 3 - THE BLUE SHARK’S DIET, BEHAVIOR, AND BIOLOGY

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CHAPTER 4 - ENCOUNTERING A BLUE SHARK

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SERIES GLOSSARY OF KEY TERMS

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INDEX

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FURTHER READING & INTERNET RESOURCES

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PHOTO CREDITS, EDUCATIONAL VIDEO LINKS, AUTHOR BIO AT A GLANCE

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KEY ICONS TO LOOK FOR:

Words to Understand: These words with their easy-to-understand definitions will increase the reader’s understanding of the text while building vocabulary skills.

Sidebars: This boxed material within the main text allows readers to build knowledge, gain insights, explore possibilities, and broaden their perspectives by weaving together additional information to provide realistic and holistic perspectives. Educational Videos: Readers can view videos by scanning our QR codes, providing them with additional educational content to supplement the text. Examples include news coverage, moments in history, speeches, iconic sports moments, and much more!

Text-Dependent Questions: These questions send the reader back to the text for more careful attention to the evidence presented there.

Research Projects: Readers are pointed toward areas of further inquiry connected to each chapter. Suggestions are provided for projects that encourage deeper research and analysis. Series Glossary of Key Terms: This back-of-the book glossary contains terminology used throughout this series. Words found here increase the reader’s ability to read and comprehend higher-level books and articles in this field.

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WORDS TO UNDERSTAND:

An animal that is at the top of its food chain and has no natural predators. Great white sharks, lions, and tigers are examples of apex predators. An environment created by humans that is different from an animal’s natural habitat, such as a zoo or aquarium. An animal cannot leave captivity unless a human allows it to leave. The long, slender fins on the underside of a shark’s body that operate as a shark’s “arms,” allowing them to propel themselves through the water.

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1 CHAPTER

INTRODUCING BLUE SHARKS

Blue sharks are found all over the world.

The most widely distributed shark in the world, the blue shark (also known as the blue dog or the blue whaler) is known for its dark blue skin on its dorsal side (and bright white skin on its ventral, or bottom, side), love of cold water, and likelihood to approach surfers, divers, and fishermen with curiosity. The blue shark is considered the most elegant of all sharks—its long, slim body, slender pectoral fins , and tendency to move slowly allow it to seemingly dance through the water.

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Since blue sharks usually travel in groups, they often appear to be dancing together as they swim. Blue sharks are not as large as some other sharks, such as great whites or tiger sharks, but they can be just as dangerous if not approached with caution. They typically do not come near the shore, so it’s unlikely for humans to encounter blue sharks unless they venture out into the deep, open ocean. The blue shark’s sharp, overlapping teeth, ability to quickly increase their speed, and countershading make them ferocious predators.

TIGER SHARK

HOW CAN YOU DIFFERENTIATE BLUE SHARKS FROM OTHER SHARKS?

Just by looking at a blue shark, it’s easy to see that they’re a little bit different than most other sharks. The dorsal (top) side of a blue shark’s body is a deep blue color, almost indigo, and a blue shark’s tail is longer on top than on the bottom, and their entire body is quite long and slender. Blue sharks have an extremely long and pointy snout that sticks out much further than its mouth and enormous pectoral fins that help the shark continually move forward (keeping ocean water moving into their mouths and over their gills, which is essential for their survival). Blue sharks also have very large eyes compared to other sharks.

SAND TIGER SHARK

SIDEBAR

BLUE SHARK

The blue shark looks different from other sharks.

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Blue sharks are found almost throughout the entire world, except in very cold areas such as the Arctic and Antarctic Circles. While blue sharks do prefer cold water, the temperature of the Arctic and Antarctic areas are simply too cold. They do not usually come near the coastline, and it’s rare to see them away from the vast open ocean, as they prefer to swim away from obstacles. Sometimes, blue sharks do swim near small islands, but it’s likely that this is unintentional. Blue sharks do not go out of their way to approach large groups of people, meaning they will not swim out of their habitat to come near the shore. This makes it difficult for scientists to learn about blue sharks—they’re simply hard to find. Scientists learn about blue sharks by tagging them, but first, they have to locate them. Scientists are currently working hard to find out more about how many blue sharks live in the wild, but since they migrate frequently, it’s difficult to know how many are left. When people come near blue sharks (on boats or diving expeditions), blue sharks are quick to interact with them, as they are very curious. Many blue sharks have never encountered a person before, due to their preference to stay away from shore. Blue sharks’ curious nature and slow movement make them ideal animals for scuba divers and cage divers to observe. Blue sharks will often swim up next to divers in an effort to learn more about them. Unlike most sharks, blue sharks do give quite a few warning signs before becoming aggressive, so it’s important that divers interacting with them keep an eye out for signs of hunting behavior. These warning signs make it possible for humans to dive with blue sharks, as they do not simply attack without giving signals. Blue sharks are not ideal in aquariums, but this is not due to their tendency to hang out in groups or their ability to become aggressive towards humans. One of the reasons that blue sharks do not do well in captivity is because they prefer to not have any boundaries to their swimming: no walls, no obstacles.

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Blue sharks prefer the open ocean.

They enjoy open, clear water. Even in the open ocean, it’s rare for blue sharks to swim in areas that are highly populated with other living things, such as coral reefs. It’s hard for blue sharks not to injure themselves when they are in an aquarium, as they run into walls and other objects. While they do have excellent eyesight, they struggle when surrounded by other animals and

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objects. In the wild, sometimes blue sharks will swim near islands, but these islands are usually small and in the middle of the ocean. It’s rare that a blue shark will come near a large land mass, such as North America. Blue sharks need lots of space to stay healthy and happy.

Watch as these brave South African divers get up close and personal with blue sharks in the open ocean! Later, you’ll learn how you can have the same experience.

While blue sharks have the ability to move quickly, they usually take things at a slow and comfortable pace. Blue sharks spend most of their time in cool water, swimming slowly, far from the coastline. They do have the ability to move quickly when it’s time to hunt, but they spend plenty of time conserving their energy in chilly waters. Blue sharks use their extremely large pectoral fins to propel them through the water as needed. These fins help sharks stay afloat and conserve energy, which is important, as blue sharks travel extreme distances during migration. Since their bodies are quite slim by nature, it’s important that their long-distance swimming does not cause them to burn lots of valuable fat that they might need during times when food is scarce. Some blue sharks have even been known to circle the globe several times over the course of their lifetimes.

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The long pectoral fins help blue sharks with their speed.

It’s common for blue sharks to approach boats, divers, surfers, and fishermen, but only when they come into the blue shark’s habitat. These beautiful creatures are not known to be aggressive towards humans unless they are provoked. There are only twelve reported blue shark attacks on humans, and four of those attacks were provoked by something that humans did. It’s scary to think about, but three of those attacks were a result of plane crashes or shipwrecks; meaning, people were in the middle of the ocean in an area where people would not normally be found. As we’ll learn, blue sharks can easily detect signals that a person or animal is struggling, and therefore, easy prey. It’s unlikely that a person would emit such signals during a scheduled dive or snorkeling trip. Blue shark attacks on humans are very rare, and they do not usually attack without warning. Blue sharks have been known to circle their prey for fifteen minutes or more before attacking, and much like great white sharks, blue sharks typically take a “test bite” of human prey before choosing whether or not to proceed with the attack. While blue sharks certainly are not considered aggressive, they also are not known for being timid. It’s a good idea to use caution when approaching blue sharks in the wild. If you’re interested in swimming with blue sharks, it’s important to do so through a licensed company that knows how to approach

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Circling is usually a hunting behavior and means you should get away.

WHY IS IT UNUSUAL FOR BLUE SHARKS TO KILL PEOPLE? Just like the great white shark, blue sharks do not seem to be big fans of the taste of people! It’s likely that humans are simply too bony for their tastes. Blue sharks prefer to eat invertebrates (animals without backbones) such as squid and shrimp, which are less bony by nature. Since blue sharks are constant swimmers, they need to prey on animals that have a lot of fat on their bodies. Human beings simply do not have enough fat to meet the dietary needs of the blue shark. Fat has far more calories than muscle or bone, and can help sustain the blue shark over its long migratory journeys. Nevertheless, blue sharks are opportunistic eaters, and do have a tendency to take a bite of whatever comes their way! Usually, when a blue shark bites a human, they realize that they’d rather swim away and find something else to eat. If a blue shark does actually prey on a human, it’s likely because the shark’s preferred food source is scarce, and they’re having trouble finding enough food to meet their caloric needs.

SIDEBAR

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