After the heavy rains large herds of ungulates move north across the Serengeti plains entering Kenya at a number of points. This mass migration is one of the biggest movements of large mammals on the planet & following hot on the heels of these grazers are large numbers of carnivores.
The geography & topography of the Masai Mara funnel & concentrate these animals creating one of the greatest wildlife spectacles in the world, yet no two years are alike. In some years the migration is early with the vanguard arriving in late June, whilst in other years numbers don't build until early August -as was the case in 2007. Various obstacles have to be crossed in this annual migration -foremost among these is the Mara river which is formidable in its own right but also holds large numbers of some of Africa's biggest Nile Crocodiles as well as wily Lion prides that know how to set a trap.
River crossings, though usually dramatic, are short-lived & capricious seeming to occur at the whim of the superherd. Sadly such a crossing did not occur during our short stay though we did get a chance to savour the spectacle of the Wildebeeste migration.