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Math,

Feeding Frenzy

Every fall, Alaskan brown bears pack on the pounds to prepare for hibernation

By Jeanette Ferrara
From the November 2020 Issue

Learning Objective: Students will use place value strategies to find the differences in bears’ weights before hibernation.

Lexile: 900L; 680L
Focus Area: Numbers and Operations,
Standards
  • CCSS: 3.NBT.A.2, MP5, MP6, MP7 TEKS: 3.4A

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Lexile® measure

  • 900L
  • 680L

Every fall, the brown bears in Katmai National Park flock to Brooks River to catch salmon. They can eat 80 to 90 pounds of food per day.

Mike Lyvers/Getty Images

Jim McMahon/Mapman®

It’s an early fall morning at Katmai National Park and Preserve in Alaska. But it’s hardly quiet. Hundreds of brown bears gather at the banks of the Brooks River. They’re about to feast at an all-you-can-eat salmon buffet. 

“I once watched a bear catch and eat over 40 salmon in a day!” says Mike Fitz, former park ranger at Katmai National Park. That’s like a person eating 400 quarter-pound hamburgers!

It’s an early morning in fall. You’re in Alaska, at Katmai National Park and Preserve. It isn’t quiet here. There are hundreds of brown bears! The bears gather at the Brooks River. They are about to feast at a salmon buffet.

“I once watched a bear catch and eat over 40 salmon in one day!” says Mike Fitz. Fitz is a former park ranger at Katmai National Park. How much food is 40 salmon in one day? Imagine a person eating 400 quarter-pound hamburgers!

Katmai National Park and Preserve/NPS  Beadnose Before); Courtesy NPS/Handout via REUTERS (Beadnose After)

Extreme Eating

For bears, gaining body fat is the key to surviving the winter. Each bear needs to increase its body weight by 30 percent before winter arrives. That’s because when temperatures drop, food becomes harder to find. 

Brown bears survive by hibernating in their dens. During this time, bears do not eat, drink, or leave their den. When they emerge in the spring, they’ve lost most of the weight and are thin and extremely hungry.

Gaining body fat is the key to winter survival for bears. Each bear needs to increase its body weight by 30 percent before winter arrives. Temperatures drop in winter. Food becomes harder to find.

Brown bears hibernate in their dens to survive. Bears do not eat or drink while they hibernate. They also do not leave their den. They come out of hibernation in the spring. They have lost most of the weight by that time. The bears are thin and extremely hungry.

Andy Rouse/NPL/Minden Pictures

Bears gain enough fat to survive hibernation by feasting during late summer and fall. During this time, the bears feel constant hunger. 

“You know that feeling of being full you get after eating a big meal?” asks Fitz. “Bears preparing for hibernation probably don’t feel that.” This allows them to eat tens of thousands of calories and gain up to 4 pounds per day!

Bears feast during late summer and fall. All of that eating helps them gain enough fat to survive hibernation. The bears feel constant hunger during these months.

“You know that feeling of being full you get after eating a big meal?” asks Fitz. “Bears preparing for hibernation probably don’t feel that.” This allows them to eat tens of thousands of calories. They can gain up to 4 pounds per day!

Celebrating Bears

Katmai’s bears have become famous thanks to an event called Fat Bear Week. During this annual “competition,” park rangers identify and photograph commonly spotted bears. They estimate how much weight the bears gain. “The bears are not tagged or handled in any way,” says Fitz.

Katmai’s bears have become famous. There is an event called Fat Bear Week. Fat Bear Week is an annual “competition.” Park rangers identify bears that are commonly seen in the park. They photograph them. They estimate how much weight the bears gain. “The bears are not tagged or handled in any way,” says Fitz.

Katmai National Park and Preserve/NPS

Fans track the weight gain of the bears through social media posts. In October, people vote for the bear they think “won” the fall feasting period. 

“I thought it would be fun if we gave the public the opportunity to compare the changes and decide who they think is the fattest bear,” says Fitz. Fat Bear Week continues to celebrate Katmai’s brown bears’ important preparation to survive the winter. 

Fans track the weight gain of the bears through social media posts. People vote in October for the bear they think “won” the fall feasting period.

“I thought it would be fun if we gave the public the opportunity to compare the changes. They could decide who they think is the fattest bear,” says Fitz. Fat Bear Week continues to celebrate Katmai’s brown bears and their important preparation to survive the winter.

VikiVector/Shutterstock.com (Salmon); ecco/Shutterstock.com (Fruit); Macrovector/Alamy Stock Vector (Nuts); Koshelev Alexey/Shutterstock.com (Acorn)

What Do Bears Eat?

Bears consume as much food as possible before winter starts. Here are some of their top foods. 

  • fish (salmon)
  • fruits and berries
  • nuts

Bears consume as much food as possible before winter starts. Here are some of their top foods. 

  • fish (salmon)
  • fruits and berries
  • nuts

Math Talk

What types of numbers are important to park rangers?

Math Talk

What types of numbers are important to park rangers?

Subtraction

What to Do

Sometimes when you subtract, you need to take away a larger number from a smaller number in one or more place value column. In this case, you can use the expanded method to help you regroup numbers, or exchange them without changing their value.

Example

Adult female brown bears tend to weigh about 296 pounds in September and October. Adult males weigh about 457 pounds during those months. How many more pounds does an average adult male brown bear weigh than an adult female during that time?

  • Write the equation you need to solve.

457 – 296 = ?

  • Use a place value chart to rewrite each number in expanded form. This will help you visualize the problem. You can’t subtract 90 from 50, so you need to regroup by borrowing from the hundreds column. Trade in 1 hundred for 10 tens and add that to the tens column.

    Now you can subtract. 
  • Add the totals in each place value column to find the solution.

100 + 60 + 1 = 161 

So, on average, adult male brown bears weigh 161 pounds more than adult females during September and October.

Subtraction

What to Do

Sometimes when you subtract, you need to take away a larger number from a smaller number in one or more place value column. In this case, you can use the expanded method to help you regroup numbers, or exchange them without changing their value.

Example

Adult female brown bears tend to weigh about 296 pounds in September and October. Adult males weigh about 457 pounds during those months. How many more pounds does an average adult male brown bear weigh than an adult female during that time?

  • Write the equation you need to solve.

457 – 296 = ?

  • Use a place value chart to rewrite each number in expanded form. This will help you visualize the problem. You can’t subtract 90 from 50, so you need to regroup by borrowing from the hundreds column. Trade in 1 hundred for 10 tens and add that to the tens column.

    Now you can subtract. 
  • Add the totals in each place value column to find the solution.

100 + 60 + 1 = 161 

So, on average, adult male brown bears weigh 161 pounds more than adult females during September and October.

Now You Try It

Use the table to answer the subtraction questions below.

Use the table to answer the subtraction questions below.

How many more pounds did Otis weigh than Divot in 2019?

How many more pounds did Otis weigh than Divot in 2019?

Compare the weights of Bear and Walker. Which bear weighed more? By how many pounds?

Compare the weights of Bear and Walker. Which bear weighed more? By how many pounds?

A. In early fall, an average adult male bear weighs 457 pounds. How many pounds heavier was Chunk? 

B. How many more pounds did Chunk weigh than Otis?

A. In early fall, an average adult male bear weighs 457 pounds. How many pounds heavier was Chunk? 

B. How many more pounds did Chunk weigh than Otis?

A. Holly won Fat Bear Week in 2019. How many more pounds did Holly weigh than Divot?

B. A classmate says that Bear weighed 25 pounds more than Divot and Holly combined. Is this true? Why or why not?

A. Holly won Fat Bear Week in 2019. How many more pounds did Holly weigh than Divot?

B. A classmate says that Bear weighed 25 pounds more than Divot and Holly combined. Is this true? Why or why not?

Continue Your Learning

  • Find a die or create a set of cards numbered 1 through 9. Roll the die 3 times or pull 3 cards to create 2 different 3-digit numbers. Subtract the smaller number from the larger number. You can draw place value charts to help you if needed.
  • Watch the video “Getting to Know Grizzlies” (above). Then go online to research more grizzly facts. Create a poster about grizzly bears using what you learned from the article, the video, and your own research. Include at least 3 number facts in your poster.

Continue Your Learning

  • Find a die or create a set of cards numbered 1 through 9. Roll the die 3 times or pull 3 cards to create 2 different 3-digit numbers. Subtract the smaller number from the larger number. You can draw place value charts to help you if needed.
  • Watch the video “Getting to Know Grizzlies” (above). Then go online to research more grizzly facts. Create a poster about grizzly bears using what you learned from the article, the video, and your own research. Include at least 3 number facts in your poster.
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