Parental investment declines with increasing age of offspring, producing a conflict between parent and offspring over amount of parental investment. The degree of parent-offspring conflict may be associated with the gender of the offspring, mating system such as polygyny, and variation in reproductive success among individuals. We examined the dynamics of maternal investment through time by observing nursing behavior in Roosevelt Elk (Cervus elaphus roosevelti). Suckling rate (P =0.031) and suckling time per bout (P =0.014) by calves decreased with calf age, and male suckling rate (P =0.047) and suckling time per bout (P =0.008) were greater than those for females. Maternal initiation of nursing was greater in the early nursing period (P =0.009), and almost all suckling bouts were terminated by the mother. Our results were similar to those of studies on other polygynous ungulate species which exhibit differences in maternal investment in offspring based on gender.