要想逃脫餓狼的追捕,，一只羊并不需要跑得比狼快,，只需要比其他羊快就行了。這是一種自私的行為,，而不是以整體利益為目的的團隊合作行為,。研究人員認為,，正是這種自私性決定了群居動物的行為。但長期以來,，關于羊群自私性的理論一直沒有得到研究數(shù)據(jù)的支持,。
現(xiàn)在，科學家們通過對羊群在躲避牧羊犬時的運動方式的分析,，證明上述理論是正確的,。這一成果刊發(fā)在《當代生物學》（Current Biology）雜志網(wǎng)絡版。為了尋求安全,，每只羊都拼命朝著羊群的中心奔跑,，而不是直接從狗的身邊跑開。
馬薩諸塞大學阿默斯特分校的生物學家Theodore Stankowich說：“對大型動物在野外的二維空間信息進行測量是一件很難的事情,。他們得益于一次獨特的機會,，在一種受控的環(huán)境中對羊群進行研究，試圖對上述問題作出解答,。”
此前,，對于海豹、螃蟹和鴿子的研究表明,，這些動物之所以群居也是出于自私的目的,，但研究者們缺乏精確的數(shù)據(jù)來證明這一點。
倫敦大學皇家獸醫(yī)學院的生物學家Andrew King和他的同事們在46只羊和一只訓練有素的澳大利亞牧羊犬身上安放了GPS系統(tǒng),，然后讓狗去看管這群羊,，同時以秒為單位記錄下每只動物的位置。接下來,，他們對數(shù)據(jù)進行分析,，以確定是什么因素影響了羊的路徑。
結果表明,，根據(jù)羊群的中心位置就可以很好地預測出羊的運動路線,。每只羊既不是以直線方式從狗身邊跑開,，也不是向各個方向散射，更不是跟隨身邊的羊,，而是全都拼命向著羊群中心跑,。當狗位于70米之外時,，羊群開始聚攏,；在它們作為一個整體向前移動時,，每只羊不斷地,、盡量地靠近中心位置,。（生物谷Bioon.com）
doi:10.1016/j.cub.2012.05.008
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Selfish-herd behaviour of sheep under threat
Andrew J. King1, , Alan M. Wilson1, Simon D. Wilshin1, John Lowe1, Hamed Haddadi1, Stephen Hailes2 and A. Jennifer Morton3
Flocking is a striking example of collective behaviour that is found in insect swarms, fish schools and mammal herds [1]. A major factor in the evolution of flocking behaviour is thought to be predation, whereby larger and/or more cohesive groups are better at detecting predators (as, for example, in the many eyes theory), and diluting the effects of predators (as in the selfish-herd theory) than are individuals in smaller and/or dispersed groups [2]. The former theory assumes that information (passively or actively transferred) can be disseminated more effectively in larger/cohesive groups, while the latter assumes that there are spatial benefits to individuals in a large group, since individuals can alter their spatial position relative to their group-mates and any potential predator, thus reducing their predation risk [3]. We used global positioning system (GPS) data to characterise the response of a group of prey animals (a flock of sheep) to an approaching predator (a herding dog). Analyses of relative sheep movement trajectories showed that sheep exhibit a strong attraction towards the centre of the flock under threat, a pattern that we could re-create using a simple model. These results support the long-standing assertion that individuals can respond to potential danger by moving towards the centre of a fleeing group [2].
