Scent urination likely serves a variety of functions, depending on the species and environment in which it is expressed. Evidence derived from observations in Denali National Park and Preserve (DNPP) suggests that scent urination by bull moose (Alces alces) is primarily directed toward females and supports the hypothesis that scent urination induces ovulation in cows. Testing of this hypothesis should be possible in captive populations. Males also appear to use urine as a means of attracting females. Female competition for a male resource is rare in mammalian mating systems, yet cow moose in DNPP aggressively compete for access to bull urine, suggesting that male urinary components may increase the probability of successful repro- duction. While priming pheromones may be required by cows to ensure birthing when calf survival will be highest, whether or not bulls produce such pheromones may be dependent on the relative benefits accrued to them. Mature bulls that scent urinate may increase reproductive success by inducing ovulation before their body condition declines and attracting cows by their scent so that courtship is possible. Subadult bull moose do not scent urinate yet attempt to acquire some of its benefits by obtaining attractive odors from mature bulls. The evolution of scent urination as an important component of moose breeding behavior may be related to the evolution of moose in the circumpolar boreal forests. Females in low-density populations may increase reproductive success by being assured of the presence of a breeding bull before ovula- tion. Use of scent urination as a mechanism to time breeding appears to be one facet of an ecological opportunist strategy employed by moose to exploit environments that are either low quality (mature boreal forests) or temporary and unpredictably distributed (seral shrub communities).