Migratory behavior is one specific behavioral mechanism many species have adopted to reduce the costs of utilizing certain resources. Environmental cues such as rainfall patterns, day length and temperature often provide the stimulus needed to trigger migratory behavior in terrestrial species. Water resource quality has been shown to affect the performance of mammals in livestock and wildlife, especially in arid environments. Poor water quality can depress milk production, food conversion, and the physiology of animals. The physiological stress of consuming poor quality water may push some mammals to seek alternative sources. In the Serengeti Ecosystem, a number of species of large mammals migrate over great distances and dramatic differences in water quality at the end of the wet season may be the trigger that propels the migration of large mammals from regions of poor water quality to regions of higher water quality.
We present data confirming substantial disparities in chemical quality between the major river basins at the end of the wet season in 2007, 2008 and 2009. The two southern most rivers in the Serengeti, the Mbalageti and Seronera, were significantly worse than those in the northern part of the ecosystem for all parameters. We discuss how the quality of these resources may be the physiological mechanism that triggers the departure of large herds of wildlife from these southern river basins. The influence of abiotic factors on migratory behavior should be considered for management strategies because growing local population and expanding tourism place further strain on surface water resources.