爬上東非大草原的一片高崗,，拿出雙筒望遠(yuǎn)鏡,，你一定會看到黑白相間的斑馬群。你或許還能看到一些瞪羚,、野牛和大象,。
對此，美國洛根市猶他州立大學(xué)的生態(tài)學(xué)家Johan du Toit認(rèn)為：“自然選擇總是喜歡混雜,。”對于自然選擇可能是這樣,，然而人類往往卻不這么想。
由于確信其他食草動物會讓自己的牛群挨餓,，肯尼亞和非洲其他地方的牧場主往往都會將它們的牲畜與野生動物分開飼養(yǎng),。然而一項新的研究卻表明，這種想法絕對是錯誤的,。野生動物,，特別是斑馬，實際上能夠幫助一個牧場興旺發(fā)達(dá)。
為了驗證農(nóng)場主的“常識”,，肯尼亞納紐基市穆帕拉研究中心的牧場生態(tài)學(xué)家Wilfred Odadi和同事對當(dāng)?shù)乜偯娣e達(dá)2萬公頃的多個牧場進(jìn)行了調(diào)查,，這里有家畜和一些被保護(hù)的野生動物，其中就包括約2000頭斑馬,。
研究人員發(fā)現(xiàn),，在旱季——這時草地會變得枯萎，野生動物似乎會對牲畜,，特別是牛群的生長造成負(fù)面影響,，后者也會大幅減少體重。然而在雨季,，這些牲畜的體重又會反彈,。他們注意到，每到這個時候,，與隔離喂養(yǎng)的牛群相比,，與野生動物一道生長的牲畜會長得更快。
研究人員在最新出版的美國《科學(xué)》雜志上報告了這一發(fā)現(xiàn),。
Odadi和同事發(fā)現(xiàn),，斑馬似乎應(yīng)該為這一結(jié)果負(fù)責(zé)。在旱季,，長頸鹿只會吃樹葉,，而大象也不會對枯草感興趣。只有斑馬——在這里到處可見的野生食草動物——會吃下其他食草動物避之不及的枯草,，這完全要感謝它們獨特的消化道,。
在這項研究中，斑馬會吃掉那些長得較高且沒有營養(yǎng)的葉片,，從而使那些更富營養(yǎng)的植被暴露出來,，并能夠吸收更多的養(yǎng)分，這也為牲畜最終的茁壯成長奠定了基礎(chǔ),。（生物谷 Bioon.com）
doi:10.1126/science.1212452
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Coexisting with Cattle
du Toit, Johan T.
Many large plant-eating mammals have evolved to live in multispecies assemblages, with species competing for food and other resources. Through domestication and animal husbandry, however, humans have enabled a few species of livestock, such as cattle, to dominate such assemblages. One standard practice in livestock production on rangelands, espoused by commercial ranchers and subsistence pastoralists alike, is the eradication of large, indigenous herbivores that are believed to compete with livestock for food. These eradication efforts have increasingly problematic implications for biodiversity conservation (1). So it is timely that on page 1753 of this issue, Odadi et al. (2) report on a relatively simple experiment that tested the assumption that cattle and wildlife compete for food. Their study, conducted in an East African savanna renowned for its large herbivore diversity, revealed that cattle do compete with herbivores such as zebras and gazelles during the dry season, when food quantity is low. In contrast, during the wet season, when food quantity is high, grazing by wildlife benefits cattle by improving the quality of forage. The findings highlight ecological processes that promote coexistence among large herbivores in grasslands and savannas, and hence could be useful for conservation
