The lush riverine vegetation of the Gremeti River is not the sort of habitat one would normally associate with big herds of wildebeest. Crocodiles are hard to find when it is in flood but there are places where they haul themselves up onto the banks and keep hidden under the vegetation. The crocs were very shy when Alan Root first started to film them and it was difficult to get anything without a long lens. But now the crocodiles here have seen more people - in fact, too many people. They've eaten two rangers in the last few years and an old poacher who operated in the area. One day a parks patrol cornered him by a big pool and he jumped in and tried to swim across. There was one big splash and that was it. When the dry season came they found his boy scouts belt buckle with the motto “be prepared” written on it. Alan usually comes here in the dry season when the wildebeest have to come to drink and the crocs have an absolute bonanza. In the wet season, however, there are a lot of catfish and the crocs sit with their mouths in the current, sensing the fish as they go past. Then they do a lightning-fast sideways strike and catch them in their mouth. The catfish have spines which they erect and lock into position, so the crocs chomp away at the spines to break them off before swallowing.