Understanding the ecology of the Desert Locust - Schistocerca gregaria (Forsk.1775) – in its solitary and transient phase is a key aspect in the improvement of locust surveillance strategy and preventive control practices. Two areas, measuring 50 x 50 km, with low and high frequencies of transient locusts, were identified in central Mauritania. Meteorology, vegetation, locust populations, and geomorphology were monitored within the two sites for two years. Perennial vegetation and a diverse geomorphology were identified as key factors that promote locust gregarization. The implications of these findings for locust surveillance is discussed.