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      Easter(复活节) is still a great day for worship,candy in baskets and running around the yard finding eggs, but every year it gets quite a bit worse for bunnies.

      And no,not because the kids like to pull their ears.The culprit is climate change,and some researchers found that rising temperatures are having harmful effects on at least five species of rabbit in the US.

      Take the Lower Keys Marsh rabbit, for instance.An endangered species that lives in the Lower Florida Keys, this species of cottontail is a great swimmer—it lives on the islands!—but it is already severely affected by development and now by rising sea levels. According to the  Center for Biological Diversity, an ocean level rise of only 0.6 meters will send these guys jumping to higher ground and a 0. 9­meter rise would wipe out their habitat(栖息地)completely.

      The snowshoe hare,on the other hand,has a color issue.Most of these rabbits change their fur color from white in the wintertime to brown in the summer, each designed to give them better cover from predators(捕食者).As the number of days with snow decreases all across the country, however, more and more bunnies are being left in white fur during brown dirt days of both fall and spring,making them an easier mark for predators.Researchers know that the color change is controlled by the number of hours of sunlight, but whether the rabbit will be able to adapt quick enough to survive is a big question. The National Wildlife Federation has reported that hunters have noticed their numbers are already markedly down.

      American pikas or rock rabbits, a relative of rabbits and hares,might be the first of these species to go extinct due to climate change. About 7­8 inches long, pikas live high in the cool,damp mountains west of the Rocky Mountains.As global temperatures rise, they would naturally migrate(迁移)to higher ground­but they already occupy the mountaintops.They can't go any higher. The National Wildlife Federation reports that they might not be able to stand the new temperatures as their habitat heats up.

      The volcano rabbit has the same problem.These rabbits live on the slopes of volcanoes in Mexico, and recent studies have shown that the lower range of their habitat has already shifted upward about 700 meters, but there are not suitable plants for them to move higher, so they are stuck in the middle.Scientists are concerned about their populations.

       Native to the US, pygmy rabbits weigh less than 1 pound and live in the American West. They are believed to be the smallest rabbits in the world. Their habitats have been destroyed by development.Several populations, such as the Columbia Basin pygmy, almost went extinct and were saved by zoo breeding programs.Pygmy rabbits also rely on winter cover by digging tunnels through the snow to escape predators, but lesser snowfall is leaving them exposed.

      All of this gives new meaning to dressing up in a giant bunny costume this Easter.

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    When people first walked across the Bering Land Bridge thousands of years ago, dogs were by their sides, according to a study published in the journal Science.

    Robert Wayne of the University of California, Los Angeles, and Jennifer Leonard of the Smithsonian Institute, used DNA material—some of it unearthed by miners in Alaska—to conclude that today's domestic dog originated in Asia and accompanied the first humans to the New World about 10,000 to 15,000 years ago. Wayne suggests that man's best friend may have enabled the tough journey from Asia into North America. “Dogs may have been the reason people made it across the land bridge,” said Wayne. “They can pull things, carry things, defend you from fierce animals, and they're useful to eat.”

    Researchers have agreed that today's dog is the result of the domestication(驯化) of wolves thousands of years ago. Before this recent study, a common thought about the precise origin of North America's domestic dog was that Natives domesticated local wolves, the descendents(后代) of which now live with people in Alaska, Canada, and the Lower 48.

    Dog remains from a Fairbanks-area gold mine helped the scientists reach their conclusion. Leonard, an evolutionary biologist, collected DNA from 11 bones of ancient dogs that were locked in permafrost(永冻层) until Fairbanks miners uncovered them in the 1920s. The miners donated the preserved bones to the American Museum of Natural History in New York City, where they remained untouched for more than 70 years. After borrowing the bones from the museum, Leonard and her colleagues used radiocarbon techniques to find the age of the Alaska dogs. They found the dogs all lived between the years of 1450 and 1675 A.D., before Vitus Bering and Aleksey Chirikov who were the first known Europeans to view Alaska in 1741. The bones of dogs that wandered the Fairbanks area centuries ago should therefore be the remains of “pure native American dogs,” Leonard said. The DNA of the Fairbanks dogs would also expose whether they were the descendents of wolves from North America.

    Along with the Fairbanks samples, the researchers collected DNA from bones of 37 dog specimens(标本) from Mexico, Peru, and Bolivia that existed before the arrival of Columbus. In the case of both the Alaska dogs and the dogs from Latin America, the researchers found that they shared the most genetic material with gray wolves of Europe and Asia. This supports the idea of domestic dogs entering the New World with the first human explorers who wandered east over the land bridge.

    Leonard and Wayne's study suggests that dogs joined the first humans that made the adventure across the Bering Land Bridge to slowly populate the Americas. Wayne thinks the dogs that made the trip must have provided some excellent service to their human companions or they would not have been brought along. “Dogs must have been useful because they were expensive to keep,” Wayne said. “They didn't feed on mice; they fed on meat, which was a very guarded resource.”