What? An aerial wildlife population survey is used in Cape Breton Highlands National Park to estimate moose (Alces alces) population density. When? Monitoring frequency for this measure occurs every two to three years. Surveys take place in early March when there is snowpack present, the weather is stable, and sightability is increased by sun angle and day length. How? The population survey uses a random stratified design. The study area is Cape Breton Highlands National Park (950km2) and is divided up into Survey Units (SU’s) or “blocks”. Survey units are numbered sequentially in rows running from west to east, beginning in the north. Stratification lines are flown along transects running through the center point of each survey unit, and cluster analysis is used to assign all survey units a moose density stratum: High, Medium or Low. Survey units are randomly selected from each stratum to be flown in the block survey. 50 survey units are initially selected (35 Low, 10 Medium, 5 High), with more survey units added as necessary to obtain a population estimate with a 90% confidence interval. Why? Moose are the top herbivore in Cape Breton Highlands National Park. Benefiting from favourable conditions following a spruce budworm outbreak and, having no significant natural predators, the moose population has become hyperabundant, resulting in negative impacts to the parks forest ecosystem. This survey every helps to monitor changes in moose density in the park, and determine if it is at a sustainable level (ie. within the natural range of variability observed in predator controlled populations).