爬上东非大草原的一片高岗，拿出双筒望远镜，你一定会看到黑白相间的斑马群。你或许还能看到一些瞪羚、野牛和大象。
对此，美国洛根市犹他州立大学的生态学家Johan du Toit认为：“自然选择总是喜欢混杂。”对于自然选择可能是这样，然而人类往往却不这么想。
由于确信其他食草动物会让自己的牛群挨饿，肯尼亚和非洲其他地方的牧场主往往都会将它们的牲畜与野生动物分开饲养。然而一项新的研究却表明，这种想法绝对是错误的。野生动物，特别是斑马，实际上能够帮助一个牧场兴旺发达。
为了验证农场主的“常识”，肯尼亚纳纽基市穆帕拉研究中心的牧场生态学家Wilfred Odadi和同事对当地总面积达2万公顷的多个牧场进行了调查，这里有家畜和一些被保护的野生动物，其中就包括约2000头斑马。
研究人员发现，在旱季——这时草地会变得枯萎，野生动物似乎会对牲畜，特别是牛群的生长造成负面影响，后者也会大幅减少体重。然而在雨季，这些牲畜的体重又会反弹。他们注意到，每到这个时候，与隔离喂养的牛群相比，与野生动物一道生长的牲畜会长得更快。
研究人员在最新出版的美国《科学》杂志上报告了这一发现。
Odadi和同事发现，斑马似乎应该为这一结果负责。在旱季，长颈鹿只会吃树叶，而大象也不会对枯草感兴趣。只有斑马——在这里到处可见的野生食草动物——会吃下其他食草动物避之不及的枯草，这完全要感谢它们独特的消化道。
在这项研究中，斑马会吃掉那些长得较高且没有营养的叶片，从而使那些更富营养的植被暴露出来，并能够吸收更多的养分，这也为牲畜最终的茁壮成长奠定了基础。（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
