Male thirteen-lined ground squirrels (Spermophilus tridecemlineatus) are subject to three forms of intrasexual competition: competition over location of spatially scattered females, overt conflict over access to those females, and sperm competition. The likelihood of both overt conflict and sperm competition varies between seasons; changes in male density, female density, and breeding synchrony were investigated as possible sources of that variability. Male density was artificially reduced mid-way through one mating season. The results of that experiment, as well as subsequent between-season comparisons, indicate that fluctuations of male density have hardly any effect on levels of overt conflict and sperm competition. By contrast, those forms of intrasexual competition are influenced strongly by female density and/or breeding synchrony.