Janzen's study of the Shahra suggested that a transhumant pattern was followed in the region based on the presence/absence of the Southwest Monsoon. Winter sites tended to be more permanent with substantial circular house foundations. Summer settlements were more ephemeral. Bertram Thomas in 1929 photographed such a Shahra summer encampment on the Taqa coastal plain. A similar pattern was observed among the Nuer in the Sudan by Evans-Pritchard.