• 2005-08-15

    * 长颈鹿的性骚扰

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    http://www.blogbus.com/newswolf-logs/1359601.html

    欠老板的两篇文章拖了一个星期,终于到了deadline前面的最后一个晚上。老板说星期一还要跟我商量新的题目,彼时手中这两篇是非交不可的了。折腾到半夜一点多终于解决了一篇,作为对自己的鼓励,先贴这儿一篇,再继续奋战下一篇吧。

    在暑假结束之前,估计我最多还会有一两篇或者两三篇的任务就要告别为农学院写news letter的闲适生活了。碌碌终日,眼看自己的暑期读书计划快要搁浅,警惕自己一下,虽不需夜夜头悬梁椎刺股,但该是抓紧时间的时候了。加把劲。

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    非常有趣的一项关于长颈鹿进食习惯的研究。母长颈鹿边吃树叶边警惕四周的动静,但他们防的不是狮子,也不是材狼,他们防的是色迷迷的公长颈鹿,因为公长颈鹿随时随地都在寻找机会进行“性骚扰”……

    Giraffes use their long, prehensile tongues to extend their reach.  Specimen at the National Museum of Natural History, Washington, DC.

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    Giraffes use their long, prehensile tongues to extend their reach. Specimen at the National Museum of Natural History, Washington, DC.
    Keeping an Eye Out
    By Gang Wu

    It is well known that vulnerable animals like monkeys are always on the lookout for predators during their eating. They may become less vigilant only when they are in a large group, with someone standing on guard.

    Giraffes, which feed on tree leaves on a land roamed by lions and hyenas, are also stopping their feeding now and then to look around. But what may be a surprise for many is that they are often not watching out for predators. Instead, they are watching one another in their own groups.

    A recent study by Elissa Cameron in South Africa’s Kruger National Park suggests that when giraffes periodically interrupt their lunch to scan their surroundings, they are mostly monitoring the whereabouts of the local male giraffes. For females and small bulls, larger bulls are the real threat on their mind.

    “The bulls are like bullies on the playground of a school, where the other kids are always trying to stay away from them,” says Cameron, assistant professor of Natural Resources and Environmental Sciences.

    Giraffe cows are sexually receptive only in varying times of year. Mature bulls, however, are constantly wandering about to try their chances for willing females. Yet most of the time, the females prefer to stay away from the hassling.

    It is interesting that female giraffes do not necessarily increase the frequency of their scanning when they are away from their group or even when their calves might be endangered by predators.

    owever, when bulls are around, the cows will often interrupt their lunch to make sure they can move away before the bulls approach.

    Younger bulls are also trying to keep a distance from larger males, simply for fear of attacks. Biologist found mature bulls are aggressive to one another throughout the year. The fight, though appearing to be graceful, can be fatal (see linked story).

    “Giraffes use their long necks to hit as clubs,” says Cameron. “The fight looks slow-motioned and graceful like ballet, but the blows are very brutal – one might be killed after being knocked down.”

    In the joint research with Johan T. du Toit of the University of Pretoria in South Africa, Cameron tried to study the foraging behaviors of giraffes, like what they are feeding on and how males are different with females in scanning their surroundings for predators.

    It turns out that the longer necks of bulls are a disadvantage rather than advantage in the scanning of their environment compared with cows. When a giraffe is reaching for higher leaves, the head is extended upwards so that the eyes are directed at the sky. As a result, the animal has to interrupt feeding regularly to scan its environment.

    The long necks of giraffes are often cited in school textbooks as a classical example of the natural selection of evolution. But that has not actually been tested. That is why Cameron and her colleagues started this project – they try to find out how natural selection shaped their behavior and they way they look.

    The above-mentioned findings published on Animal Behavior journal this summer are the first few in Cameron’s project. More outcomes are expected as the project goes on, she says.

     

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