As rivers leave the mountains behind, they gradually warm and begin to support more life. Indian rivers are home to the world's most social otter. Smooth-coated otters form family groups up to 17 strong. Group rubbing not only refreshes their coats, but strengthens social bonds. When it comes to fishing there is real strength in numbers. Fishing practice begins when the cubs are four months old. Only the adults have the speed and agility needed to make a catch. Adults share their catches with their squabbling cubs. Most otters are solitary, but these rich warm waters can support large family groups and even bigger predators. Mugger crocodiles, four metres long, could easily take a single otter. But, confident in their gangs, the otters will actively harass these great reptiles. Team play wins the day.


河流离开高山以后水温逐渐升高，水中的生物也逐渐增多。印度的河流中生活着世界上最多的群居水獭。这些毛皮光滑的水獭结伴生活，一群的数量最多可达17只。大家互相磨擦不但会让皮毛更干净，而且也能增进相互之间关系。捕鱼的时候数量优势清楚地显示出来。小水獭四个月大就开始学习捕鱼。只有成年水獭才有捕鱼所需的速度和灵活性。成年水獭和吵嚷的孩子们一起分享猎物。绝大部分水獭都单独生活，但在这些温暖的水域里有充足的食物，它们可以成群生活。甚至更大的食肉动物也是如此。沼泽鳄的身长可达4米，可轻易抓住一只水獭。但结成群体之后，这些水獭不停地围攻这些大型爬行动物。团队的力量取得了胜利。