PLANET EARTH Freshwater

These botos（亚马逊河豚，产于亚马逊河和奥里诺科河的南美洲海豚。其颜色从亮粉色到灰色不一而同，这种颜色的变化取决于海豚的年龄和环境因素：如阳光、水温和水压等） are huge - two and a half meters long. In these **murky waters **（浑水）they rely on sonar（声纳） to navigate（导航） and hunt. They work together to drive shoals of fish（鱼群） into the shallows. Botos are highly social and in the breeding season there is stiff competition（激烈竞争，stiff做副词时表示很，非常的意思） for mates. The males hold court in a unique way. They pick up rocks in their jaws and flaunt（炫耀，类似于show off） them to their attending females. Maybe each male is trying to show how strong and dexterous（身手敏捷） he is and that he therefore is the best father a female could have for her young.