Macoun’s arctic (Oeneis macounii) is a biennial satyrine butterfly found predominantly in boreal forests of North America. I monitored populations of O. macounii in Riding Mountain National Park (RMNP) in 2011 and in Sandilands Provincial Forest in 2012. I captured, sexed, marked and took UTM coordinates of butterflies to compare population sizes, sex ratios, longevity, dispersal and behaviour. I measured habitat variables around capture sites at RMNP, to establish environmental characteristics associated with butterfly occurrence. Population estimates at Sandilands show that the population size there is robust, but could not be calculated at RMNP. The number of butterflies observed at RMNP suggests that the population there is small and localized. In RMNP, males were more often in forested sites with sunny clearings, while female encounter sites were dominated by grasses, suggesting sexual segregation. The data collected from this survey is important for conservation strategies for the declining population at RMNP.