A Whale of an Ocean

Flesch-Kincaid Reading Level = 4.7

In the warm waters off the coast of Africa, a blue whale has just given birth. The baby is already twenty-six feet long and weighs six thousand pounds. She grows around eight pounds every hour. The mother weighs as much as twenty elephants. Yet she is starving.

Why doesn’t the mother blue whale grab a quick snack? Quite simply, there is no food for her here. She will survive on her thick coat of blubber. In a few months, she will take her calf to their feeding grounds at the bottom of the world, the Southern Ocean that surrounds Antarctica.

Before whale hunting nearly wiped them out, there were well over two hundred thousand blue whales living off Antarctica. By the time the slaughter stopped, there were fewer than a thousand left.

Why would any animal seek out the cold waters at the bottom of the world? The answer is simple: food. Blue whales are the largest animals on Earth. Yet they are adapted to eat just one kind of prey. That prey is a two-inch long animal called krill.

Krill eat tiny living things called phytoplankton. Phytoplankton float at the surface of the Southern Ocean. They use the energy of sunlight to make food. The krill eat the phytoplankton, and the blue whales eat the krill. It’s one of the simplest food chains on Earth.

Blue whales are known as baleen whales. Instead of teeth, baleen whales have flexible bristles (called baleen) in their mouths. They use these bristles like a spaghetti strainer. When blue whales find a large school of krill, they gulp enormous mouthfuls of krill and water, then push the water back out with their tongues. The baleen traps the krill inside, just as a spaghetti strainer traps noodles. The whale then swallows the krill. Yum!

But what makes these waters in the Antarctic so special that they were once home to such a huge concentration of the largest animals on Earth? There are two explanations. One is that the Earth is tilted, and the other is that cold water sinks.

Most places on Earth have regular cycles of day and night all year. At the North and South Poles, however, the tilt of the Earth means that each pole has both days and nights that last for months. In the Antarctic summer there is plenty of sunlight for the phytoplankton to make their food. But there is sunlight elsewhere, too. What else makes the Southern Ocean special? The answer is cold water.

Water is a little like air. Just as warmer air will rise above cooler air (think of a hot air balloon), warmer water rises above cooler water. In the tropics, where the Sun heats the water by day, warm water stays at the surface, while the colder water remains below.

In that deep water are nutrients that could help phytoplankton grow. But there is no sunlight there. The phytoplankton cannot grow. At the surface, there’s plenty of sunlight, but few nutrients. What’s a phytoplankton to do?

The Southern Ocean is different. It doesn’t get as hot as the tropics. So even though there’s a lot of sunlight, the water doesn’t get warm. The cold water from the surface sinks down, pushing the deeper, nutrient-rich water back up. This means there are both lots of sunlight and lots of nutrients in the same place. With plentiful sunlight and plentiful nutrients, the phytoplankton grow like crazy! The krill population explodes. The whales come to feast.

Or they once did. In the days before whaling, the Southern Ocean was alive with great whales. Some approached one hundred feet in length. In a single generation, human beings hunted these giant animals to the very edge of extinction. Today, while the blue whale is protected from hunters, its numbers remain low. A blue whale mother has just one calf every two to three years. At that rate, it will take many years for the blue whales to recover. But in time, perhaps, the whales in their thousands will again dine on krill in their millions at the bottom of the world.

Glossary

baleen – stiff, flexible bristles inside a whale’s mouth

krill – small, shrimplike animals that live in the ocean

phytoplankton – small floating plants

Modified versions of this text are available for grades K-1 (Flesch-Kincaid Reading Level = 1.9) and grades 2-3 (Flesch-Kincaid Reading Level = 2.6). See below for links to all three versions in text, book, and electronic book forms.

Printable Files

Notes for assembling the books:

You can put this book together a couple of different ways. You can print out the pages, cut them in half and then order the pages back to front. Fold the stack in half and then staple the spine of the book. Pairs of pages can then be stapled or glued along the right edge.

You can also assemble the book as a foldable book.

To assemble the book this way, print the four pages and align the document pages so that the following book page numbers are in the lower right-hand corner: front page, page 6, page 2, and page 4. (The cover page should be on top and page 4 on the bottom.) Set your copier to copy single pages into double pages and run the four document pages in the order specified. Cut along the dotted line in the center of the double-sided page, place the book pages in order, fold, and staple along the spine.

Electronic Books

A Whale of an Ocean

Grades K-1 Electronic Book
Articulate Version
Flash Version

Grades 2-3 Electronic Book
Articulate Version
Flash Version

Grades 4-5 Electronic Book
Articulate Version
Flash Version

In the Articulate version, click on the small arrow at the top of each page for the narration. The large arrow at the right will take you to the next page.

In the Flash version, the play button (in the top right hand corner) will play an audio file of the text on that page, while the pawprint (bottom right hand corner) will turn to the next page. Please note that the audio files take a moment to load on each page. Once the file has been loaded, a play button will appear in the top right hand corner of the page. To minimize the delay on each page, you can open the file and read through the article first. Once each page’s audio has loaded, it remains loaded until you close the browser window. By preparing the article ahead of time, you can have students start at the beginning of the book and read without delays. If you don’t have Flash, you can download it for free from the Adobe web site.

Related Activities

Reading and Writing About Whales Using Fiction and Nonfiction Texts
The lesson uses the nonfiction picture book Big Blue Whale by Nicola Davies to present factual information about blue whales and the fiction picture book Dear Mr. Blueberry by Simon James to demonstrate how a letter can be used to ask questions and foster inquiry about blue whales.

Planet Ocean: Blue Whale
Background information about the blue whale. Suitable for independent reading by upper elementary students; useful for teachers of primary students.

Why Do Whales Make Sounds?
Students will learn about the vocalizations of several whale species and the special calls of different populations of blue whales. They’ll be asked to learn snippets of whale calls and to simulate whales trying to locate each other in the ocean. The students will conclude by drawing pictures of whales vocalizing and by writing captions explaining what their pictures show.

Whale Lesson
This short description combines two separate activities – simulations of whale blubber (using plastic bags and shortening) and the difference between baleen and toothed whales (using combs, toothbrushes, and pepper).

Whales Unit (Grades K-3)

Whales Unit (Grades 4-8)
Interdisciplinary units focusing on whales’ characteristics and adaptations.

Literacy Templates

Use these templates to engage your students as they develop comprehension and recall skills. For more information, please see “Active Participation: Ensuring Student Engagement.”

Find the Question for “A Whale of an Ocean” (Grades 2-3)

Find the Question for “A Whale of an Ocean” (Grades 4-5)

Literacy Set
Download everything you need to use this activity in your class: a pdf version of this article, “A Whale of an Ocean” illustrated books, and the Find the Question templates.