The Masai Mara rcosystem includes the Masai Mara National Reserve and the adjacent and excellent Mara private conservancies (Mara North, Naboisho, Olare-Motorogi, Olderkesi being the prime ones). One of the  highlights of the Masai Mara National Reserve is the annual wildebeest migration crossing rivers between the Serengeti and the Masai Mara. It is the largest mass movement of land mammals on the planet – with more than a million animals following the rains. But the Mara River crossing poiunts can be very crowded between July and October, when this happens.  The selection of camp is very important to avoid being with many dozens of other vehicles. During this time, it is better to stay in a concession, with limnited tourist and vehicle numbers, to enjoy the abundant wildife in these superbly run private conservancies, and have a day trip to the Mara River if one really wants to try and see a river crossing. There are also a few conservancies located close to the Sand River, which give a much more exclusive and intimate experience, should the wildebeest and zebra chose to cross when you are there.