Stressed-out sheep bleat out their anguish, U.S. researchers reported. They found that, like humans, sheep communicate stress by changing the timbre of their voices.

• 美国研究人员说，不堪重负的绵羊会用叫声诉说苦闷。他们发现，绵羊和人一样会通过改变声音的音色来抒发压抑的情绪。