参考文本

All dolphin species, young dolphins aren't born with the skills necessary to defend for themselves. In fact the mortality rate for dolphin calves is 50% in the first year. What they are born with is the ability to mimic and mirror whatever their mother does, and this is how they learn to survive. The calf becomes mom shadow, imitating her every move, pose, posture and action. If mom stands upon her tail, so does her calf. Come on, parents. Don't you wish you could get this kind of cooperation?

Of all the skills that a mom has to teach junior, the most important one is how to find food. She gives the instructions with sound like this. When fish hear her, they run for cover, burrowing themselves into the sand. The dolphins then utilizes what's called echolocation－a kind of dolphin sonar system where their voice echoes back-giving them a clear idea what fishy delights to lie beneath the surface. As mom looks for food, her calf continues to mimic her every move.

Another technique for the young ones to master －hydroplaning in the shallows. These dolphins rock along at tremendous speeds. Their bodies half in and half out of the water. Now watch just how effective this technique is for catching fish. Oh, gotta! Effective, yes, but not all dolphins have mastered the art of hydroplaning. And those who have get that showed off for them. They toss the catching, play with it, and they parade it under water, too. Now, why doesn't another dolphin try to grab it? This might be a ritual to establish trust, or maybe the other dolphins just wanna avoid getting in a fight. So this is the last thing the dolphin calf learns from mom. Playing with your food is not only OK; it gives you status with your fellow dolphins.

（transcribed by sophieann）

mortality rate
number of deaths within a given period of time