Forced to find new river crossing points in the Serengeti-Mara region of Eastern Africa, the wildebeest descend into individual despair and collective chaos. Fast currents and steep banks all but deny escape onto the tree-covered banks. New arrivals try unsuccessfully to scramble over the lead group that cannot climb quickly enough onto the available dry ground. Such scenes may become more common as the Great Migration faces more variable climate and narrower corridors from changing land-use. (Photo and caption by Karen Lunney/National Geographic Photo Contest)

(via 2013 National Geographic Photo Contest - Photos - The Big Picture - Boston.com)

Forced to find new river crossing points in the Serengeti-Mara region of Eastern Africa, the wildebeest descend into individual despair and collective chaos. Fast currents and steep banks all but deny escape onto the tree-covered banks. New arrivals try unsuccessfully to scramble over the lead group that cannot climb quickly enough onto the available dry ground. Such scenes may become more common as the Great Migration faces more variable climate and narrower corridors from changing land-use. (Photo and caption by Karen Lunney/National Geographic Photo Contest)

(via 2013 National Geographic Photo Contest - Photos - The Big Picture - Boston.com)