Resource pulses come in many forms, including mast seeding by conifers in northern systems. Masting is thought to be an adaptation by trees to increase seed escapement by swamping seed predators. Red squirrels are the dominant seed predator for spruce but they have developed their own adaptation whereby they are able to anticipate mast years. The anticipation by squirrels and changes in their density lead to some very interesting patterns of selection that lead to various life history traits and behaviours being favoured at different points in the masting cycle. The Kluane Red Squirrel Project has followed over 10,000 individual red squirrels over 25 years to try to sort out the winners and losers in this highly dynamic system. I will describe some of our findings and the results of a 10 year experimental evolution experiment designed to understand how resource pulses drive micro-evolution in this system.