Recognising a mother's call is one of theearliest and most important life lessons for a dolphin calf.

对小海豚而言，辨别母亲的呼唤是它们最早、也是最为重要的功课。

They can easily be separated from theirmothers in the vast open ocean, so listening out for her call means they couldquickly reunite.

在浩瀚的大海中，它们很容易就会和母亲分离，因此，留心倾听母亲的呼唤意味着它们能很快再次会合。

But just how early a calf learns itsmother's call was not fully understood. In a new study of bottlenose dolphins,researchers listened in on two captive dolphin mothers to understand howmother-calf recognition develops.

但是，小海豚到底多大就能学会听母亲的呼唤，我们还不十分清楚。在一项对宽吻海豚（bottlenose dolphin）的最新研究中，研究人员对两位圈养的海豚妈妈进行监听，试图了解海豚妈妈和小海豚之间的辨识是怎样建立的。

They discovered that the mothers rapidlyincrease their unique "signature whistles" as soon as the calf isborn. They whistle up to five times more than usual. But they also saw themothers do something completely unexpected.

他们发现，小海豚刚一降生，海豚妈妈很快就能发出独特的“唿哨信号”。她们发出的唿哨要比平时多出五倍，但是，研究人员也发现了海豚妈妈一些完全出乎他们意料的做法。

We were surprised at how strong the resultswere, says Stephanie King of the University of Western Australia, who led theresearch at the Dolphin Research Center, a sea pen facility in Florida, US.

西澳大利亚大学研究人员斯蒂芬妮·金（Stephanie King）负责领导海豚研究中心的这项研究。该中心是设在美国佛罗里达州的一个海笔（sea pen）研究设施。她表示，“我们对研究结果颇感意外。

We call this 'vocal imprinting', where thecalf imprints on its mother’s signature whistle, says King.

斯蒂芬妮·金表示，“我们将小海豚要学会的妈妈唿哨信号中的印记称为‘声音印记’。”

It's an important learning phase where thecalf learns to recognise its mother, and it's important this happens quicklybefore mother-calf separations occur.

“小海豚学习辨别自己的妈妈是个重要的学习阶段，在和海豚妈妈分离前，小海豚就进入这个阶段非常重要。”

It was already known that it takes a calfseveral months to develop its own unique call. "They are not born with asignature whistle, they learn it," says King.

目前已经得知，小海豚要花好几个月时间才能学会发出自己独特的呼唤。斯蒂芬妮·金表示，“海豚并非生来就会发出唿哨信号，而是后天学会的”。

Until they do so, they have to listenclosely to find their mothers.

在学会发出唿哨信号前，它们不得不仔细听妈妈的唿哨声才能找到妈妈。

This work, published in the journal MarineMammal Science, reveals once again how vital sound is to a dolphin's world.

该项目的研究成果发表在《海洋哺乳动物科学》杂志上，这再次揭示了声音在海豚世界的重要性。

Two weeks after the calves were born asurprising turn of events took place.

海豚妈妈偷窃其他小海豚的情况十分罕见。

It is rare for a female dolphin to stealanother's calf

小海豚出生两周后，一件令人意外的事情发生了。