托福og2听力Why does the professor mention the time she spent on a boat doing research? 答案解析

[00:00.00]Listen to part of a lecture in a biology class.
[00:03.90]Professor: We’ve been discussing animal communication. [00:07.13]Um, today we’re going to talk about dolphins. [00:10.11]Now, dolphins make a wide range of communicative sounds and also display something called vocal learning, which is the ability of an animal to modify its vocalizations based on its experience with other animals.
[00:26.76]Ah, there are many types of dolphin vocalizations. [00:30.32]We, we still don't know their precise meanings一partly, I suppose, because we haven't really tried that hard to figure out their precise meanings-but we do know that dolphins use vocalizations as a way of communicating with one another. [00:44.41]And we’ve categorized their vocalizations into three types: whistles, clicks, and burst pulses. [00:51.97]The dolphin whistles are very high-frequency sounds, ah, partially above the range of human hearing. [00:58.87]What’s fascinating is, each dolphin has a signature whistle, which is unique to each individual dolphin. [01:06.88]It allows them to call to and identify each other, [01:11.31]Jennifer?
[01:12.85]Female Student: Kind of like learning someone’s name? [01:15.38]So ... do dolphin parents choose names for their children?
[01:19.45]Professor: Well, again that’s something we don’t know, but we do know that no two signature whistles sound identical. [01:27.11]And, members of the same family, their signature whistles have similar elements. [01:32.93]Dolphins use them as contact calls-ah, they they call to each other while traveling and foraging. [01:40.04]It helps keep the group together, and helps mothers and children find each other. [01:45.19]Think of it like ... ah, if you were traveling in the forest with one other person who was just out of sight, you’d call out, "Are you there?“ and the other person would respond. [01:57.95]But if there were several people in the forest, you would have to call that person's name to call to them.
[02:04.19]In, in addition to whistles, dolphins produce clicks, which are actually sonar or sound waves. [02:11.32]They use the clicks to communicate, but, more importantly, to navigate and hunt. [02:17.41]How? Well, the sonar clicks bounce off objects, and then the dolphins convert the incoming signals into a three-dimensional picture ... a, a mental map ... of what's around them. [02:30.65]The clicks are extremely sensitive and accurate. [02:34.14]The sonar clicks are also very strong. [02:36.67]And there's this theory that one reason dolphins swim side by side is to avoid interference from each other's sonar clicks. [02:45.25]Interference would be confusing ... it would prevent them from getting an accurate picture of their surroundings. [02:51.54]Ah, and what's interesting is, dolphins will turn off their sonar when another dolphin passes in front.
[02:58.72]Ah, the third category of dolphin vocalizations is burst pulses. [03:05.09]These are all this other sounds the dolphin makes-squawks, squeals, barks, groans, and so on. [03:13.45]Burst pulses are used to display aggression, show dominance, and attract a mate. [03:20.44]But whistles, clicks, and burst pulses aren't the only ways dolphins communicate. [03:25.52]Um, does anyone remember any other ways?
[03:28.68]Male Student: In the book, it said that they also slap their tails against the water. [03:32.34]Oh, and ... the air that comes out when they breathe or whistle ... the ... ah ... the bubble streams? [03:37.10]They can control how the air bubbles come out. [03:39.61]I thought that was really interesting.
[03:41.28]Professor: Yes ... the bubble streams are very interesting. [03:44.78]Dolphins can identify and locate each other by their bubble streams, and they can imitate the bubble stream patterns of other dolphins . .. sort of like saying hello. [03:55.76]So as you can see, dolphins use many different sounds and behaviors to convey messages to each other.
[04:03.15]I’d like to tell you about when I was a graduate student... and ... I spent one summer on a boat in the Atlantic Ocean studying marine life. [04:11.59]One morning there were about 25 dolphins swimming with the boat. [04:16.58]We could hear their clicks and whistles as they called to each other. [04:20.30]Now, we were there as impartial scientists, to do research, but…how could we not notice the beauty as the bubble streams made patterns in the water and the dolphins appeared to dance and play? [04:33.60]It's wonderful when you do fieldwork and actually experience something you've been studying in a classroom. [04:39.35]So if you ever have the opportunity ... go for it.