Out in the Cold.
On a cold winter day, a snowshoe hare hops through a Montana forest. Suddenly, it hears a noise that sounds like a predator. The hare freezes. If it sits perfectly still, the predator might not see it and go away.
Weeks ago, the hare shed its brown summer coat and grew white fur. The color acts as camouflage, hiding the hare in the snow. But there's a problem: Winter has been warmer than usual this year. There isn't any snow on the ground, and the hare is perfectly visible.
Snowshoe hares are facing this problem more often. In recent years, the average global temperature has been increasing. Many areas receive less snow than they once did. As a result, more and more hares don't match their surroundings, says Scott Mills, a biologist at the University of Montana.
Mills is studying snowshoe hares and other northern animals that turn white in the winter. His big question: As the climate warms and snow becomes scarcer, can these animals survive?
Snowshoe hares live in forests across the northern U.S. and Canada (see Snowshoe Hare Range, page 13). They're a food source for many animals, such as owls, coyotes, and bobcats, "We call them the candy bars of the forest," says Mills.
In the summer, brown coats help the hares blend in with the forest floor. As winter approaches, the changing amount of sunlight triggers a process inside the hares' bodies. They begin molting, or changing coats. First the tips of a hare's ears and nose lose their color, followed by its back and shoulders. After about six weeks, the animal is all white.
But snow is falling less often and melting more quickly in areas where hares live. That makes the animals easy to spot. "It's like a white light bulb sitting on a brown carpet," says Mills.
Predators have a much easier time catching prey that stand out. Mills and other scientists recently tracked snowshoe hares in Montana. They found that hares that didn't match their environments were less likely to survive the winter. In some areas, such as in parts of Wisconsin, snowshoe hare populations are shrinking.
Snowshoe hares aren't the only animals that turn white in the winter (see Color Changers, below). Arctic foxes grow white fur to hide from predators like golden eagles. The color also helps them sneak up on lemmings and other prey. Some species of lemmings, weasels, and caribou also make the seasonal switch.
In a world without snow, white winter coloring can have deadly consequences for all of these animals. And when one species disappears from an area, many others are affected. If prey animals become scarce, predators may go hungry Without predators, prey populations can grow out of control.
Despite the threats, scientists have hope for the color-changing animals. In January 2014, biologist Laura Gigliotti was tracking snowshoe hares in Pennsylvania. She expected the hares to have completely white coats. She was surprised to spot some hares that were partly or completely brown.
Scientists think that skipping the color change is an adaptation. Over many generations, some hares have become browner to help them survive in areas with patchy snow.
That's good news for the entire species, says Mills. If the brown hares survive better than the white ones, they'll pass genes for staying brown to their offspring. Over time, more and more hares will stay brown year-round.
To make sure that happens, Mills wants to conserve areas where the brown and white hares mix. By protecting those places from human development, people can boost the odds that the color-changing animals will adapt to climate change. "It's a hopeful part of the story," says Mills.
words to know
camouflage--body shape or coloring that conceals an animal
molting--shedding hair, feathers, or a shell
population--a group of animals or plants of the same species living in one place
adaptation--a change in the body or behavior of a species over many generations, making it better able to survive
genes--molecules inside cells that are passed from parent to offspring and determine an organism's traits
Scientists know of 21 species that change from brown to white in the winter. Here are son animals living in North America that make the switch.
PEARY CARIBOU: Peary caribou live in northern Canada and Greenland. They grow white fur in the winter to hide from predators like wolves.
ARCTIC FOX: These small foxes live in the frozen northern tundra. White camouflage helps them sneak up on lemmings and other prey.
Think: How does camouflage help predators like foxes survive
LONG-TAILED WEASEL: In the northern U.S. and Canada, these animals grow white winter coats to avoid being noticed by both predators and prey.
WHITE-TAILED PTARMIGAN (TAHR-mi-guhn): These are the only birds that turn white for winter. The color hides them eagles hunting above.
Snowshoe Hare Range
Snowshoe hares live across the northern U.S. and Canada. This map shows the hares' winter colors in different parts of their range.
Think: Scientists want to protect places where white and brown hares mix together. Based on this map, which areas should they choose?
Out in the Cold
READING LEVELS: Lexile 880 / Guided Reading Level R
NEED A LOWER READING LEVEL? To access this article at a lower reading level, go to scholastic.com/superscience.
Analyze data from an investigation to explain how changes in seasonal camouflage affect an animal's ability to survive.
Core Idea: LS4.C: Adaptation
Practice: Analyzing and interpreting data
Crosscutting Concept: Stability and change
Reading Informational Text: 3. Explain events in a text, including what happened and why.
Science: 3.10A, 4.10A, 5.10A
ELA: 3.61, 4.61, 5.61, 6.51
(1) Use a sidebar to prompt a discussion.
Log onto SuperScience's website and open the magazine view of pages 12-13. Use the spotlight tool to highlight the images in the sidebar "Color Changers." Have students make observations about the images. Ask: How would each animal's color help it survive?
(2) Read the article and review it with a skills sheet.
Have students read the article independently and complete the "Think It Through" skills sheet (T10). Then ask: How does the color of a snowshoe hare's coat affect its ability to survive in the summer? What about in the winter?
(3) Conduct an investigation to simulate how predators locate prey in different environments.
Divide the class into pairs. Give each pair a white sheet of paper, a sheet of newspaper, 30 newspaper circles and 30 white circles (made with a hole punch), tweezers, and a timer.
One student in each pair acts as a predator and turns around. The other student places the white sheet of paper on a table and spreads the newspaper circles and white circles over it. The circles represent prey animals.
The predator uses tweezers to pick up as many circles as possible in 15 seconds. Students count the types of circles collected and record the results in a data table. Have them do this again two more times.
Repeat the investigation with the sheet of newspaper on the table. After everyone has finished, ask:
* What patterns do you notice in the data?
* What do the patterns tell you about how easy it is for predators to find prey in different environments?
(4) Analyze a map.
Have students work independently to complete the skills sheet "Hare Homes" (T7). Then discuss answers as a class. Ask: As snow disappears, what do you think will happen to the range of the other animals from the sidebar that also change colors in the winter?
available at scholastic.com/supersclence
Hare Homes (T7): Use a map to answer questions about where snowshoe hares live.
Think It Through (T10): Answer critical-thinking questions about the article.
Close Reading (online only): Reread the article to answer dose-reading questions.
Video: Amazing Adaptations (online only): Learn about how animals use adaptations to survive in their habitats.
Caption: Snowshoe hares that don't match their surroundings are easy for predators to spot.
Caption: SUMMER: Brown fur helps the hares blend in with the forest floor.
Caption: WINTER: The hares' fur turns white, helping them hide in the snow.
Caption: Students watch as biologist Scott Mills releases a hare after studying it.
Caption: Radio collars allow scientists to track hares in the wild.
In "Out in the Cold" (pp. 10-13), you learned that scientists want to protect places where white and brown showshoe hares mix together. The map below shows the hares' winter colors in different parts of their range. Study the map, then answer the questions below.
SNOWSHOE HARES' WINTER COLORS
1. Which country shown on the map is NOT home to snowshoe hares?
(C) United States
(D) all of the above
2. In the northeastern U.S., what color are snowshoe hares in the winter?
(A) All are brown.
(B) All are white.
(C) Some are brown and some are white.
(A) all of the above
3. Use the compass to describe where showshoe hares stay brown in the winter.--
4. If global temperatures continue to rise, how might a future map showing the range of snowshoe hares look?--
* Hare Homes (Reproducible, T7)
1. b 2. c 3. In the winter, snowshoe hares stay brown in the western continental U.S., western Canada, and southern Alaska. 4. Answers may include that the hares may move northward where it's colder in the winter and that more hares might stay brown year-round.
Think It Through
Use the article "Out in the Cold" (pp. 10-13) to answer each question.
1. Which sentence from the article best explains how warmer winters are affecting snowshoe hares?
(A) "If [the hare] sits perfectly still, the predator might not see it and go away."
(B) "There isn't any snow on the ground, and the hare is perfectly visible."
(C) "In recent years, the average global temperature has been increasing."
(D) "Snowshoe hares live in forests across the northern U.S. and Canada."
2. What natural occurrence causes snowshoe hares to molt and change color in the winter?
(A) a decrease in temperature
(B) a change in the amount of sunlight
(C) an increase in snowfall
(D) an increase in the number of leaves that fall from the trees
3. Explain how camouflage is an adaptation that helps snowshoe hares survive.--
4. How is camouflage beneficial to both predators and prey?--
5. If snowshoe hares disappear, how might that affect plants and other animals that live in the same area? Use details from the article in your answer.--
* Think It Through (Reproducible, T10)
1. b 2. b 3. Snowshoe hares change the color of their coats every winter to hide from predators. 4. Camouflage helps a predator because it prevents the predator from being seen, which makes it easier to attack prey. Camouflage helps prey because it makes it harder for predators to find it. 5. If snowshoe hares disappear, their predators, such as owls, coyotes, and bobcats, may go hungry and their populations may decrease. Without snowshoe hares, the plants that they eat could grow out of control.
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|Title Annotation:||life science; snowshoe hares|
|Date:||Dec 1, 2018|
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