Foraging behaviour in East Asian desert rodents and its implications on coexistence

We studied the foraging behaviour of two sympatric rodents (Meriones meridianus and Dipus sagitta) in the Gobi Desert, Northwestern China. The role of the foraging behaviour in promoting species coexistence was also examined. We used giving-up densities (GUDs) in artificial food patches to measure the patch use of rodents and video trapping to directly record the foraging behaviour, vigilance, and interspecific interactions. Three potential mechanisms of coexistence were evaluated (1) microhabitat partitioning; (2) spatial heterogeneity of resource abundance with a tradeoff in foraging efficiency vs. locomotion; and (3) temporal partitioning on a daily scale. Compared to M. meridianus, D. sagitta generally possessed lower GUDs, spent more time on patches, and conducted more visits per tray per capita, regardless of microhabitat. However, M. meridianus possessed advantages in average harvesting rates and direct interference against D. sagitta. Our results only partly support the third mechanism listed above. We propose another potential mechanism of coexistence: a tradeoff between interference competition and safety, with M. meridianus better at interference competition and D. sagitta better at avoiding predation risk. This mechanism is uncommon in previously studied desert rodent systems.