Winter begins in the north on December 22nd. People and animals have been doing what they always do to prepare for the colder months. Squirrels (松鼠), for example, have been busy gathering nuts from trees. Well, scientists have been busy gathering information about what the squirrels do with the food they collect.

They examined differences between red squirrels and gray squirrels in the American state of Indiana. The scientists wanted to know how these differences could affect the growth of black walnut (黑胡桃) trees. The black walnut is the nut of choice for both kinds of squirrels. The black walnut tree is also a central part of some hardwood forests.

Rob Swihart of Purdue University did the study with Jake Goheen, a former Purdue student now at the University of New Mexico. The two researchers estimate that several times as many walnuts grow when gathered by gray squirrels as compared to red squirrels. Gray squirrels and red squirrels do not store nuts and seeds in the same way. Gray squirrels bury nuts one at a time in a number of places. But they seldom remember where they buried every nut. So some nuts remain in the ground. Conditions are right for them to develop and grow the following spring. Red squirrels, however, store large groups of nuts above ground. Professor Swihart calls “death traps for seeds”.

Gray squirrels are native to Indiana. But Professor Swihart says their numbers began to decrease as more forests were cut for agriculture. Red squirrels began to spread through the state during the past century.

The researchers say red squirrels are native to forests that stay green all year, unlike walnut trees. They say the cleaning of forest land for agriculture has helped red squirrels invade Indiana. Jake Goheen calls them a sign of an environmental problem more than a cause.

The Beagle Brigade

Return to the United States from a trip abroad ,and your luggage will get inspected by the Beagle Brigade, a team of beagles and their human partners. Working with human partners, the beagles sniff out potential threats to American agriculture.

An orange or apple, for example, might have a Mediterranean fruit fly. Hams could carry a disease such as hog cholera. These and other pests could destroy farmers' crops and livestock. " Once we introduce something   that   is not part of the environment, there may not be any controls of it in the environment," notes Lisa Davis at the National Dog Detector Training Center in Orlando, Florida. "The best thing for us to do is prevent it from coming across the border and becoming established. "

When a beagle sniffs specific food smells, it signals its partners by siting there. The human officer then investigates. When the dog is right ——which happens 90 percent of the time ——it gets an edible（可食用的） treat.

"The dog is not out there working," explains Davis. " It's out there playing. It's a game to the dog. "The handlers give the beagles plenty of food and love. They make sure they get first-class medical attention, too. When the dogs finally retire after 9 to 11 years ,they will find caring homes for them. It's a dog's life indeed!

Their people partners work and study somewhat harder. As specialized quarantine（检疫） officers,most hold degrees in the biological sciences or related sciences.

How well does the Beagle Brigade do its job? " On average," notes Davis, " each year our 54 teams prevent around 75,000 prohibited , restricted items. Since even one infected item could cause widespread destruction, that's a great result for America's agricultural environment.

Last year I 【小题1】 (work) in Nepal for three months. When I had a few days off，I decided 【小题2】 (go) into the jungle (丛林) . I asked a Nepalese guide，Kamal Rai to go with me.

We started our trip at six in the morning with two elephants 【小题3】 (carry) our things. It was hot, but Kamal made me wear shoes and trousers to protect me 【小题4】 snakes. In the jungle there was a lot of wildlife, but we were trying to find tigers. We climbed onto the elephants' backs to see better. However, 【小题5】 is unusual to find tigers in the afternoon because they sleep in the daytime.

Then, in the 【小题6】 (distant), we saw a tiger, and Kamal told me to be very quiet. We moved nearer and found a dead deer, 【小题7】 was the tiger's lunch! Suddenly, I started to feel very 【小题8】 (frighten), then a huge tiger jumped out suddenly. It caught Kamal's leg between its teeth, but I managed to pull Kamal away. One of our 【小题9】 (elephant) ran at the tiger and made it go back into the grass, so we 【小题10】 (quick) ran away.  That night it was impossible to sleep!

   Penguins are the number-one attraction for many visitors to Antarctica. If you go on a ship that is allowed to make shore landings, you may see them. But to get a close look at penguins, you have to be smart.

First of all, keep in mind that Antarctica’s visitor rules require that you remain at least five meters away from the penguins in order not to disturb them. You could easily become responsible for the death of a little penguin or the destruction of an egg if your too-close presence should disturb a penguin parent.

If a penguin is trying to move away from you, you must stop what you’re doing and back off even if you’re farther than five meters away. However, the rules don’t prevent a curious penguin from approaching within five meters of you — as long as the bird makes the move, not you.

Little penguins, in particular, are quite curious. I’ve seen several lucky tourists who were astonished to find that little penguins came right up to them. If a penguin comes extremely close to you, remember that you are not allowed to touch or hold it.

Here are more tips for getting close to penguins.

Ignore the smell: where penguins live is filled with guano（海鸟粪）and the smell takes some getting used to.

Be quiet because loud noises make penguins nervous. Fast or sudden movements signal meat — eating animals to penguins, and they react accordingly, so slow down when you walk around them.

Since it may take half an hour or more before the penguins get used to you, you need to be patient. Put away your camera — too often people are so focused on getting the pictures that they forget to look with their own eyes, but most of your most memorable experiences in Antarctica will be marked in your mind, not on a roll of films.

   Dragging a sleigh loaded with enough presents for the world’s children can be no easy skill. But, since ancient times, the Christmas Eve duty has been performed by a team of beloved reindeer.

Soon, however, Santa Claus may have to start looking around for a stronger type of animal, as newresearch shows the species is becoming increasingly puny. A 16-year survey on the arctic Norwegian islands, Svalbard, found the reindeer there have declined in weight by an alarming 12 percent.

The reduction in average body weight is being blamed on global warming. In the research presented lately at a meeting of the British Ecological Society in Liverpool, scientists have explained how upward temperatures are robbing female reindeer of nutrients during important periods of pregnancy.

Snow in Svalbard typically covers the ground for eight months of a year, which, combined with low temperatures, limits grass growth to June and July. But as summer temperatures increase by around 1. 5℃, grass has become more productive, allowing female reindeer to gain more weight by autumn and therefore to have more babies. However, winters have brought with them greater rainfall which freezes when it settles on the snow. Reindeer can often access the poor food sources beneath the snow by clearing it away with their antlers (鹿角) , but they cannot break through the hard ice. As a result, female reindeer are becoming starved, causing them to lose their babies or give birth to the much lighter young.

Despite the findings, reindeer appear to be suffering less from the effect of climate change than some other arctic species. Last week the scientists warned that a third of the world’s polar bears could disappear in the next 40 years.