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New technology is putting the focus on rarely witnessed aggression between two of the fiercest predators in North America. For the last few decades, populations of cougars and bears have been on the rebound. But until recently, researchers didn't know how these formidable predators interacted.
To improve their understanding of these potential heavyweight matches, scientists set up motion-sensitive cameras in British Columbia, where both species are increasing in number. The researchers rigged the countryside so that black bears wandering the shorelines of Vancouver Island would trigger the playing of recorded sounds of cougar growls over loudspeakers. Video cameras captured the bears' reactions—which were not timid.
"They almost invariably approached the sound source and in many cases did so in sort of an aggressive manner." Justin Suraci, an environmental studies researcher at the University of California, Santa Cruz, involved with the research.
This aggressive behavior manifested in different ways. Mother bears were the feistiest, with six moms actually charging the cougar sounds and one even biting a speaker. On the other hand, solitary bears moved towards the speakers making a huffing noise often associated with aggression.
Suraci says that the cougar sounds could represent an easy opportunity for the bears to make a food heist. Cougars in the area often cache the seals and sea lions they kill and come back to them for days. But bears will seek these meals out, driving the big cats away from their leftovers. The research is in the journal Ethology.
The findings help researchers get a better idea of how populations of large predators will interact as they recover on the landscape.
"There's a lot of research suggesting that when you've got a whole suite of these larger apex predators, cougars, wolves and bears for instance in North America, they're not all essentially on equal footing." And the interactions that determine who's on top are full of sound and fury.
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新技术将焦点放在北美两大最凶猛食肉动物间的罕见攻击行为上 。过去几十年来，美洲狮和熊的数量一直在回升 。但是直到最近，研究人员才知道这些强大捕食性动物的互动方式 。
为了加强对这些潜在重量级较量的理解，科学家在不列颠哥伦比亚省设置了动作感应相机，这两个物种在该省的数量都在增加 。研究人员将相机安装在乡村地区，这样一来，黑熊在温哥华岛海岸线上闲逛时就会触发扬声器，播放美洲狮的吼叫声 。摄像机拍下了黑熊的反应——它们并不害怕 。
“它们几乎总会走近声源，许多时候还会展现出咄咄逼人的架势 。”贾斯汀·苏拉奇是加州大学圣克鲁兹分校的环境研究员，他也参与了此项研究 。
这种攻击性行为以不同的方式显现出来 。熊妈妈的脾气是最暴躁的，实际上，有6只母熊向美洲狮的声音发起了攻击，有1只母熊甚至咬住了扬声器 。另一方面，落单的熊会走近扬声器，并时常发出挑衅性的怒吼 。
苏拉奇表示，对熊来说，美洲狮的叫声可能意味着它们能轻易抢走食物 。这一地区的美洲狮经常把它们捕杀的海豹和海狮藏起来，过几天再回来取食 。而熊会找到美洲狮藏起来的食物，并把美洲狮赶走 。这项研究结果发表在《动物行为学》期刊上 。
“许多研究表明，当一个地方有很多大型顶级掠食者时，以北美为例，美洲狮、狼和熊的地位并不平等 。”而在争夺顶端位置的互动行为中，经常充斥着吼叫声和怒火 。
谢谢大家收听科学美国人——60秒科学 。我是约书亚·拉普·勒恩 。
1. set up 创建；建立；安排；组建；
例句：I set up the computer so that they could work from home.
2. seek out 寻找到；找出；
例句：We are trying to seek out the trouble spot of the instrument.
3. a suite of 一系列；一套；
例句：He has composed a suite of music for the film.
4. be full of 有大量…的；满是…的；
例句：Weegee's photographs are full of artfulness, and artifice.