A new study suggests the singing noises made by humpback whales(座头鲸) might be a sign of loneliness. Scientists who recorded humpback whales 'behavior in Australia discovered that fewer whales made the singing noises, also called wailing, as their population grew. "Humpback whale song is loud and travels far in the ocean," said marine biologist Rebecca Dunlop of the University of Queensland in Brisbane. She has long studied humpback whales and helped lead the new study. Her work has centered on humpbacks that reproduce near Australia 's Great Barrier Reef. Dunlop told The Associated Press she made an unexpected finding as whale numbers sharply rose following the end of commercial whaling(捕鲸). "It was getting more difficult to actually find singers," she said. Dunlop added, "When there were fewer of them, there was a lot of singing—now that there are lots of them, there is no need to be singing so much." Scientists first began to hear and study the complex songs of the humpback whales in the 1970s. They used underwater microphones to do so. Only male whales sing. Eastern Australia 's humpback whales came close to disappearing in the 1960s when their number dropped to around 200. But over time the population began to regrow, climbing to about 27,000 whales by 2015. That number is near estimated pre-whaling levels. As the density of whales increased, their singing behavior changed. While 2 in 10 males made wailing noises in 2004, 10 years later the number had dropped to 1 in 10, Dunlop said. The team 's study appeared in a recent issue of Nature Communications Biology. Dunlop said she thought singing played a big part in bringing in mates when populations were severely reduced. "It was hard just to find other whales in the area because there weren 't many," she added. "When humpbacks live in denser populations, males looking for mates also have to deal with competing whales." Dunlop explained the singing noises might bring in other possible mates. The research suggests the seas are still noisy with humpback whale sounds. Many humpbacks seek to bring in mates with a combination of singing and physical movements, the study notes. The large increase in the humpback population during the study period provided valuable data about changes in the animals 'behavior, said Simon Ingram. He studies humpback whales at the University of Plymouth in Britain. Ingram said humpback whales must have been singers long before whaling reduced their number. But the new study demonstrates how necessary their complex and beautiful songs were for their survival and recovery.1、 According to Paragraph 1, humpback whales make singing noises probably to ______.look for foodattack rivalslead other whalesexpress emotions2、 According to Paragraph 3, what can we learn about Dunlop 's finding? ______All the whales are good singers.Humpback whales are too lazy to sing.Commercial whaling helps protect the Great Barrier Reef.More humpback whales lead to the reduction of singing noises.3、 Why do male humpback whales sing? ______Because it can help them find mates.Because it can attract other male whales.Because it can resist commercial whaling.Because it can damage underwater microphones.4、 What 's probably Dunlop 's research field? ______Ocean biology.Animal science.Physical science.Commercial whaling.5、 According to Simon Ingram, humpback whales ______.stop singing after the whaling ends in Plymouthrely on their songs for their survival and recoverychange their singing behavior constantly in Britainmake more singing noises with the help of scientists