The common spiny mouse (Acomys cahirinus) inhibits the foraging activity of the golden spiny mouse (A. russatus). These two sympatric species of spiny mice, which are considered habitat competitors, occur in extreme arid environments. To test this theory of competition, the influence of urinary odors of both conspecific and heterospecific mice on the foraging behavior of A. russatus was studied under controlled laboratory conditions. Twenty adult males, born in captivity and unfamiliar to the odors of the donor mice, were tested in 3 experimental conditions choosing between 2 seed patches that were scented with urine of either heterospecifics (A. cahirinus), conspecifics (A. russatus) or controls (odors of the tested individual). Of the 20 males, 12 were also tested with urine of unfamiliar gerbils, bushy-tailed jird, considered as competitors in the field. Both conspecific and heterospecific urine samples from Acomys significantly reduced foraging behavior of A. russatus when compared to the control odor. The inhibitory effect of the Acomys urine does not result from the novelty of chemical stimuli of the urine because no effect was shown with unfamiliar gerbil urine. The findings are in accordance with the general theory that A. cahirinus dominates the foraging activity of A. russatus. We hypothesize that chemical cues in the urine of Acomys spp. might induce a negative effect on the foraging behavior of A. russatus.