Lesson 23 dolphins拓展（课件）-2023-2024学年剑桥少儿英语二级下册

Dolphins Dolphin Dolphins are marine mammals closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, eating mostly fish and squid. Risso's Dolphin bottlenose dolphin Orca Killer Whale Commerson's dolphin Dusky dolphin Indo-Pacific hump-backed dolphin Sousa chinensis Behavior Intelligence Dolphins are often regarded as one of Earth's most intelligent animals, though it is hard to say just how intelligent. Comparing species' relative intelligence is complicated by differences in sensory apparatus, response modes, and nature of cognition. Social behavior ＊Dolphins are social living in pods of up to a dozen individuals. In places with a high abundance of food, forming a super grouping may exceed 1,000 dolphins. ＊Dolphins can establish strong social bonds; they will stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if needed. Sleeping Generally, dolphins sleep with only one brain hemisphere in slow-wave sleep at a time, thus maintaining enough consciousness to breathe and to watch for possible predators and other threats. Vocalizations Roughly three categories of sounds can be identified: frequency modulated whistles burst-pulsed sounds clicks. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to the way human vocal cords function and through burst-pulsed sounds. Jumping Dolphins occasionally leap above the water surface, and sometimes perform acrobatic figures. Scientists are not certain about the purpose of the acrobatics. Possibilities include locating schools of fish by looking at above-water signs like feeding birds, communicating with other dolphins, dislodging parasites or simple amusement. Playing Play is an important part of dolphin culture. Dolphins play with seawee