The Kluane Red Squirrel Project is an interdisciplinary, large-scale field experiment designed to test the importance of food abundance to the ecology and evolution of red squirrels. The project is based in the southwest Yukon of Canada, where red squirrels have been studied extensively since 1987. In this part of their range, the seed of white spruce cones (Picea glauca) is a critical food resource for red squirrels. White spruce is a masting species, which means that these trees produce extremely high numbers of cones every 2-6 years with few cones produced in the intervening years. Individual red squirrels, therefore, are likely to experience both very high and very low levels of food within their lifetime. Research performed for almost 30 years has indicated that yearly variation in the abundance of spruce cones has important ecological and evolutionary consequences.