Resource dispersion influences mammalian mating systems by affecting space use by females and in turn the strategies employed by males. Other elements related to mating interactions, however, also may affect female decisions, and it usually becomes difficult to discriminate between them. Here we present the results of experimental food supplementation during rut in the red deer (Cervus elaphus hispanicus). We provided food at 2 levels of spatial dispersion in order to test whether changes in the distribution of food within a short period of time affect spatial behavior of females or other features of the mating system. Food clumping produced an increase in local density of females using an area and in the size of female groups. It also produced an increase in number of adult males, male–male interactions, and male harassment toward females. Despite the overall rate of harassment being higher with food clumping, females received a lower per capita rate of harassment because they gathered into much larger harems. Variance in harem size increased with higher levels of food clumping. Our data show that females were highly sensitive to food distribution when joining harems, which stresses the relative importance of direct benefits (food and sexual harassment avoidance) in molding the conditions under which selection operates during rut in Iberian red deer.