泛滥之谜 07-英语听力

[00:00.01]The labyrinth of papyrus provides food and shelter for enormous numbers of fish. [00:05.51]These waters are clearly fertile [00:08.09]But did they nourish the faraway fields of Ancient Egypt? [00:12.18]The world of papyrus is always on the move. [00:16.21]Air sacs in the stem give it great buoyancy. [00:19.37]Huge papyrus rafts drift on the current. [00:23.60]These restless islands of reeds constantly redefine the channels of the waterways. [00:28.69]It's no wonder explorers found the Sudd impenetrable. [00:32.35]A healthy population of dangerous animals [00:35.09]also helps maintain the Sudd's inhospitable reputation. [00:38.97]At this time of the year, the huge swamp is, in fact, shrinking. [00:44.81]Fish become more densely concentrated, making them easier prey. [00:49.54]But it's not just the water that's becoming overcrowded. [00:52.95]White-eared kob retreat into the dwindling grasslands [00:56.19]of the Sudd during the dry season. [00:58.35]When they were last counted, there were thought to be a million of them [01:02.14]One of the greatest concentrations of large animals on Earth [01:05.66]1,000 per square kilometre. [01:08.69]But the overcrowding encourages strange behaviour. [01:11.82]The males are forced to fight over females [01:14.47]by protecting tiny, merely symbolic, territories. [01:18.08]But they aren't the only ones [01:19.32]for which the White Nile is a lifeline in the dry season.