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Arctic Fox: Remarkable Color-Changing Adaptation — Reading Comprehension

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Grades

Standards

MS-LS2-4
RI.6.3
RI.7.3
RI.8.8

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This NGSS-aligned passage (MS-LS4-4) examines the Arctic fox's remarkable seasonal color change from winter white to summer brown. Students discover how photoperiod triggers hormonal changes that control fur pigmentation, demonstrating natural selection in action. The text explains the survival advantages of camouflage against predators and prey, with discussion of climate change impacts on this adaptation. A fun fact reveals their fur provides such insulation that they don't need to increase metabolic rate in cold. Comprehension questions target the mechanisms and evolutionary advantages of seasonal camouflage, while vocabulary questions clarify 'metabolism' in extreme environments. Ideal for teaching about heredity, adaptation, and climate change impacts on Arctic species.

CONTENT PREVIEW

Vulpes lagopus in Iceland (cropped 2) — "Vulpes lagopus in Iceland" by Jonathen / Wikimedia Commons.

The Arctic fox (Vulpes lagopus) is one of nature's most remarkable examples of seasonal adaptation. Living in the harsh tundra where temperatures can plunge below -50°F (-45°C), this clever survivor has evolved an incredible trick—its fur changes color with the seasons!

In winter, the Arctic fox sports a thick, snow-white coat that blends perfectly with the icy landscape. This camouflage helps it sneak up on prey like lemmings and ptarmigans while hiding from predators such as wolves and polar bears. Come spring, as the snow melts, the fox sheds its white fur for a brown or grayish coat, matching the rocky tundra and summer vegetation. This color shift isn't just for show—it’s a matter of survival. A fox that stays white in summer would stand out dangerously, while one that stays brown in winter would struggle to hunt unseen.

But how does this color change work? It's all in the fox's genes and environment. Decreasing daylight in autumn triggers hormonal changes that stimulate white fur growth, while increasing sunlight in spring reverses the process. This adaptation has been refined over thousands of years through natural selection—foxes with better camouflage survived longer and passed on their traits.

Climate change, however, is disrupting this perfect system. With shorter winters and less snow, white foxes sometimes stick out against bare ground, making hunting harder. Meanwhile, red foxes are moving northward, competing for food and territory. Scientists worry that if warming continues, the Arctic fox’s camouflage may become less effective, threatening its future.

Fun Fact: An Arctic fox’s winter coat is so insulating that it can withstand freezing temperatures without increasing its metabolic rate—unlike most mammals!

Why does the Arctic fox's fur turn white in winter?

To attract matesTo blend with snowTo repel insectsTo absorb sunlight

What triggers the Arctic fox's seasonal color change?

Temperature shiftsChanges in daylightFood availabilityRain patterns

How does camouflage help the Arctic fox in winter?

It keeps the fox warmerIt hides the fox from predators and preyIt makes running through snow easierIt helps the fox swim in icy water

What is a major threat to the Arctic fox’s camouflage today?

Too much snowClimate change reducing snow coverOverhunting by humansThicker fur growth

What color is an Arctic fox’s summer coat?

Pure whiteBlack and whiteBrown or grayReddish-orange

How does natural selection relate to the Arctic fox’s camouflage?

Foxes choose their fur colorBest-camouflaged foxes survive and reproduceHumans bred them for color changesAll foxes change color at the same time