Animals’ Early Warning Systems

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Massive migrations

 

Wildlife photographer Mike Blair remembers the day he witnessed how waterfowl can sense change in the weather. That morning the weather was mild, with a few snow geese on the marshes at the wildlife refuge. But as the day progressed, flight after flight of geese crossed the sky and settled on the wetlands. The next day temperatures plummeted and a snowstorm hit.

 

“The refuge staff said there were 20,000 geese there at the start of the day,” says Blair. “By the end of the day, they were estimating there were 300,000 or more.”

 

Wildlife biologists believe migrating waterfowl have a built-in sense to detect the approach of large storms and are particularly responsive to changes in barometric pressure.

 

Fishing frenzy

 

When Steve Hogan pulled out his fishing tackle, he wasn’t expecting great things. He had fished the same pond for years and never caught a bass weighing more than 2 pounds. “I thought it was just one of those ponds where the bass were stunted,” he says.

 

That day a nasty front approached. The skies turned dark and lightning could be seen in the distance. The dramatic change in weather produced a day of fishing Hogan will never forget. He and a friend caught and released more than 70 bass in a short period, many of them 3 to 5 pounds.

 

Other fishermen have had similar experiences. Lure manufacturer Tom Mann talks about the day he was out fishing and sighted a tornado.

 

“The fish just went crazy,” he says. “They ... just bit everything. It obviously had to do with that rapid change in [barometric pressure].

 

“Now, I’m not telling people to be out on the water before a tornado comes in. That’s dangerous. But it does show how these big storm systems will affect fish.”

Vocabulary Focus

plummet (v) [5plQmit] to fall very quickly and suddenly

stunted (adj) [5stQntid] preventing the growth or development of something from reaching its limit

tornado (n) [tC:5neidEu] a strong, dangerous wind that forms itself into a spinning cone and is able to destroy nearly

anything in its path as it moves across the ground

 

Specialized Terms

barometric pressure (n) 大气压力 the pressure caused by the weight of the air as recorded by the barometer, a device that measures air pressure and shows when the weather is likely to change; also called “atmospheric pressure”

tackle (n) 全套装备或用具 all the objects needed for a particular activity

front (n) 锋面 the place where two masses of air that have different temperatures meet

lure (n) 钓饵 an artificial insect or other small animal that is attached to the end of a fishing line to attract fish

动物预警系统

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大举迁移

野生动物摄影家迈克·布莱尔还记得当天亲眼目睹了水鸟如何察觉到气候的转变。那天上午的天气温和，野生动物保护区的湿地上只有少数的雪雁。但随着一天慢慢过去，成群的雪雁飞过天际，都来这里栖息在湿地上。第二天温度骤降，暴风雪来袭。   

“保护区的工作人员说那天刚开始时有2万只雪雁，”布莱尔说：“到了深夜，他们估计那有30万只或更多的雪雁。”   

野生动物生物学家相信随季节迁移的水鸟有一种与生俱来的感应能力，可以察觉到大风雪的前兆，并对大气压力的变化特别有反应。

 

狂乱的垂钓场面   

史帝·霍根取出他的钓具时，并没期待会有什么好事；多年来，他都在这个池塘钓鱼，从来没钓过超过2磅的鲈鱼。“我以为像有些池塘一样，这里的鲈鱼就是发育不良的那种。”他说。

当天，一道恶劣的锋面袭来。天色变暗，远处还看得到闪电。这天天气的戏剧性变化带给霍根一次永远难忘的钓鱼经荡。他和朋友在短短的时间内，钓上来又放走了70多条鲈鱼，其中很多都重达35磅。

其它垂钓者也曾有过类似的经历。钓饵商人汤姆·曼恩提到有一天外出钓鱼时目睹一场龙卷风的经过。

“鱼简直都疯了！”他说：“它们……什么饵都吞，显然跟（大气压力的）快速突变有关。”

“我可不是在鼓励人们龙卷风来袭前还参与亲水活动，那样太危险了。不过以上情况真的可以显示大风暴系统对鱼群的影响。”