Until recently,the only large mammal known to produce seismic signals was the elephant seal,a species whose notoriously aggressive bulls slug it out on beaches around the world for possession of harems of females.

• 直到最近，人们所知的能够发出地震信号的大型哺乳类动物只有海象。其极富攻击性的雄性在全世界的海滩上为了争夺妻妾而相互争斗的特性是广为人知的。