Migration!

 Tuesday September 3

Often when people talk about the Great Migration, they have in mind the vast herds of wildebeest (gnu) crossing the Mara River is treacherous circumstances. Crossing the Mara may be the most dramatic element, but the Great Migration is much more than that; it comprises a full twelve months cycle of movement, primarily by 1.5 million wildebeest but also including other antelope species. The motivation for the migration is rainfall and fresh green grass. While species like zebras can digest any kind of grass, wildebeest are very particular and need the tender new shoots and clean drinking water. New grass sprouts are a function of rainfall, but also are a function of natural (originally) or controlled (now) burning.  The rains come to the southern part of the Serengeti in October to December, so the herds migrate to the south in January and have their babies in February, staying until  April. The rains come to northern Serengeti and the Masai Mara in the spring, and in general there is more rain in the north because of the influence of Lake Victoria. The herds start a long circular migration west and then north, crossing the Mara in August through October. But as both sides of the Mara have green grass in that season, some herds have changed their routes and are still crossing from south to north in September, even though  the traditional model would say they should all be in the Masai Mara already.  This whole migration cycle is one of the seven wonders of the natural world. And we got to see some of it today!

Early in the morning, we drove 2 hours back to the Seronera airstrip and flew for 30 minutes to an airstrip north of the Mara but still in Tanzania. We noticed, first from the plane and then from the ground, how much more green everything was here compared to where we have been the past three days. We also immediately noticed that there were wildebeest everywhere—- small family groups, big herds, isolated older males.

There are 12 “established” crossing sites along the Mara. We drove west from the airstrip along the river, watching the herds on the southern shore for signs they were going to cross. The collective noun for wildebeest is “confusion” and it seemed an apt description today. We watched as herds combined into massive groups. Some individuals would wander down to the river bank and then change their minds and go back up. There were large processions of the animals moving single file to the west and then they’d turn around and go east again. 

We watched for about two hours. Then suddenly, for no apparent reason, they decided to go. A phalanx of animals came down to the river, entered the water and started swimming across, fighting the current and avoiding the rocks. More and more animals entered, creating traffic jams mid-stream.  New entry points, some involving jumping down the bank, were created. Multiple exit points on the northern shore (our shore) were used to scramble back up to the grasslands. Sometimes a wildebeest would balk at entering the water and the line would halt—- until a new leader emerged and the flow went on. We watched for 25 minutes, with an estimated 2500 wildebeest crossing in front of us. We only saw two fall prey to a crocodile.  It was truly an unforgettable experience. 

Our new camp is a bit more “camping than flanking” but is still very comfortable. It started raining as we settled in before dinner, another new experience for us. 

Pictured: the crossing, the midstream congestion snd the leapers.