ENVIRONMENT

As the climate warms, snowshoe hares are increasingly ditching their winter wardrobes and keeping the brown fur they sport during the rest of the year. Now, a new study shows how: by borrowing a gene from a jackrabbit. (Science)

Why does the snowshoe hare change coats to begin with? Check out our terrific gallery of downloadable illustrations for some help.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit. Teaching camouflage or natural selection next year? This might be a good one to bookmark.

Discussion Ideas

• The first sentence of the academic article says “Snowshoe hares molt from a brown coat to a white coat in winter.” What is molting?
  • Molting describes the process of animals shedding fur, skin, feathers, or other body covering. Among species of insects, other arthropods, and reptiles, molting is sometimes called ecdysis. Many animals molt:
    • Snakes molt several times a year, as they outgrow and shed their skin.
    • Insects molt as they outgrow and shed their exoskeletons. In some species, such as butterflies, the final stage of molting transforms the animal’s entire body.
    • Birds molt at least once a year as they shed old feathers and groom new ones.
    • Dogs molt twice a year as they shed their coats.
    • Frogs molt as often as once a day when they shed their skin—and eat it.

 

• Why do snowshoe hares and other Arctic animals molt to a pretty white coat in the winter? Take a quick look at the “camouflage tactics” section of our reference resource for some help.
  • The snowshoe hare’s winter coat is a classic camouflage tactic: background matching. In background matching, a species conceals itself by resembling its surroundings in coloration, form, or movement.
    • In summer, the snowshoe hare’s ruddy brown fur resembles rocky terrain or a forest floor. In winter, that terrain is covered with a thick layer of snow and the snowshoe hare resembles the snowy landscape.
    • Background matching helps camouflage the snowshoe hare from predators including lynxes (their main predator), foxes, weasels, and birds of prey such as owls, hawks, and eagles.

 

• Over the last several years, fewer snowshoe hares are molting from brown to their traditional winter white. Instead, they are molting from brown to … brown. Why?
  • natural selection. Climate change has meant the winter blanket of snow is coming later and later in the year. (Learn more about the impact on snowshoe hares here.) Snow-white bunnies are very easy for predators to spot on a brownish hillside or plain. Snowshoe hares with the adaptation of a brown-to-brown molt are more likely to survive and, uh, breed like rabbits.

 

• The Science article associates the brown-to-brown molt with a gene borrowed from the snowshoe hare’s big-eared cousin, the black-tailed jackrabbit. Why doesn’t the black-tailed jackrabbit molt to winter white?
  • The black-tailed jackrabbit’s other name—the desert hare—gives it away. Unlike the snowshoe hare, the black-tailed jackrabbit inhabits ecosystems that stay warmer all year and are less likely to be covered in snow for months at a time. Like the snowshoe hare, however, the black-tailed jackrabbit’s coat is an excellent example of background matching: its blackish-brown and speckled-white coat beautifully matches its habitat.

 

• How did snowshoe hares “borrow” the jackrabbit agouti gene, which prevents coats from turning white?
  • Snowshoe hares acquired the agouti variant the old-fashioned way—interbreeding.

 

TEACHERS TOOLKIT

Science: How the snowshoe hare is losing its white winter coat

Nat Geo: Camouflage illustration gallery

Nat Geo: Before and After: See Animals Change Their Coats for Winter

Nat Geo: What is camouflage?

(extra credit!) Science: Adaptive introgression underlies polymorphic seasonal camouflage in snowshoe hares