1. Patterns of male reproductive allocation provide insight into life-history characteristics. The trade-offs associated with resource and female group defense are well-defined. However, less is understood about trade-offs in species that practice scramble-competition polygyny, where successful strategies may favor competitive mate-searching rather than contest competition and fighting. 2. White-tailed deer (Odocoileus virginianus) practice scramble-competition polygyny where solitary males search for and assess receptivity of females scattered across the landscape. Physically mature males are expected to do most of the breeding because of the high energetic costs of reproduction and high social status. However, young males may collectively sire one-third of offspring. To gain a better understanding of trade-offs associated with scramble-competition polygyny, we quantified metrics associated with reproductive effort and success. 3. We quantified changes in body mass of harvested males, energetic costs of locomotion based on movements of GPS radio-collared males, and timing of reproduction via temporal genetic parentage assignments. 4. Young males (1.5 and 2.5 years old) sired offspring, but their mating success was mainly limited to peak rut, when most females were in estrus. Furthermore, multiple paternity was common, indicating opportunistic reproduction. Reproductive effort, indexed by body mass loss, was highest in prime-age males (5.5-6.5 years old). Surprisingly, young and post-prime males also exhibited significant body mass loss, indicative of investment in reproductive effort. Movement rates increased 2 to 4-fold during rut as a function of mate-search activities, but cost of locomotion would cause only about one-third of observed body mass loss. Because males are capital breeders, we infer most of body mass loss is due to reduced foraging. 5. In scramble-competition polygyny, the repeated location of potential mates and assessment of their estrous status appear to be important constituents of male mating strategies. Therefore mating success may be influenced by time management and spatial memory, and not based solely on social dominance. Thus, reproductive effort should be greater for individuals capable of reducing time foraging. For those that cannot, opportunistic mating opportunities may arise when operative adult sex ratios are low. Our analyses reveal valuable insight into the trade-offs associated with scramble-competition polygyny.