英语听力：《恐龙的战争》3 顽强防御—14
What was a surprise is the higher centers of their brain are very large and suggest that something very different is going on in Parasaurolophus and its kin than in most other of these plant-eating dinosaurs.
But how does an advanced auditory cortex help a Parasaurolophus defend itself against monster carnivores? First of all, its acute hearing can detect an approaching predator from kilometers away. Then most importantly, it can react, deploying an unusual weapon, a distinctive sound that originates deep inside a strangely shaped head crest.
The crest contains the animal’s nasal cavity—a tube that loops around twice, creating a chamber two and a half meters long. Calls, vibrations originating in the voice box travel along these tubes. Like the chambers of a trombone, those tubes amplify and lower that sound. The result—an extremely low-frequency hum, even deeper than a foghorn.
Each species has its own distinct shape. Each species would have its own distinct sound.
The arrangement of the chambers inside each animal is unique. And the sound they create is like a fingerprint. These calls are Parasaurolophus’ primary form of defense. They are communicative, social beings that live in herds. Parasaurolophus have learned there’s safety in numbers.
An isolated Parasaurolophus would be a dinosaur in trouble. It’s gonna have to look out for predators on its own. And therefore, a lone individual might do its call to say, “I’m alone”, and wait to hear for…
