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BMC Biology：羚羊用特殊方式展示自己
來源:科學(xué)時(shí)報(bào)

羚羊據(jù)美國《科學(xué)》雜志在線新聞報(bào)道，有很多方法能讓對手和伴侶留下深刻印象，雄獅會(huì)長出濃密而巨大的鬃毛，孔雀會(huì)展示它們美麗的羽毛，雄鹿則會(huì)晃動(dòng)頭上粗大的鹿角。而非洲大羚羊的招數(shù)可謂更加巧妙——它們會(huì)像人類捏響指關(guān)節(jié)一樣讓膝蓋發(fā)出“啪啪”的響聲。研究人員在11月出版的《BMC生物學(xué)》雜志上報(bào)告了這一發(fā)現(xiàn)。這種聲音在幾百米之外都能聽到，它取決于羚羊的大小和力氣。羚羊個(gè)頭越大，“啪啪”聲也就越響——恐怕沒有哪個(gè)家伙愿意和這樣的對手過不去。（創(chuàng)賽新聞中心 canspecsci.com）

    創(chuàng)賽推薦原始出處：
BMCBiology，doi:10.1186/1741-7007-6-47，Jakob Bro-J?rgensen，TorbenDabelsteen
Knee-clicks and visual traits indicate fighting ability in elandantelopes: multiple messages and back-up signals
Jakob Bro-J?rgensen and Torben Dabelsteen
Background
Given costs of signalling, why do males often advertise theirfighting ability to rivals using several signals rather than justone? Multiple signalling theories have developed largely in studiesof sexual signals, and less is known about their applicability tointrasexual communication. We here investigate the evolutionarybasis for the intricate agonistic signalling system in elandantelopes, paying particular attention to the evolutionaryphenomenon of loud knee-clicking.
Results
A principal components analysis separated seven male traits intothree groups. The dominant frequency of the knee-clicking soundhonestly indicated body size, a main determinant of fightingability. In contrast, the dewlap size increased with estimated agerather than body size, suggesting that, by magnifying thesilhouette of older bulls disproportionately, the dewlap acts as anindicator of age-related traits such as fighting experience.Facemask darkness, frontal hairbrush size and body greyness alignedwith a third underlying variable, presumed to be androgen-relatedaggression. A longitudinal study provided independent support ofthese findings.
Conclusion
The results show that the multiple agonistic signals in elandreflect three separate components of fighting ability: (1) bodysize, (2) age, and (3) presumably androgen-related aggression,which is reflected in three backup-signals. The study highlightshow complex agonistic signalling systems can evolve through thesimultaneous action of several selective forces, each of whichfavours multiple signals. Specifically, loud knee-clicking isdiscovered as an honest signal of body size, providing anexceptional example of the potential for non-vocal acousticcommunication in mammals.
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