Cannibalism, which functions as a life history trait in at least 1300 species of both invertebrates and vertebrates, plays important ecological and evolutionary roles in populations. During times of low resource availability, cannibalism of juveniles by adults can redirect reproductive energy to times of higher resource availability. For example, prolonged increases in sea surface temperature depress marine food webs and lead to increased egg cannibalism among glaucous-winged gulls (Larus glaucescens); consumption of a single cannibalized egg provides almost half the daily energy needs for an adult gull. Motivated by the glaucous-winged gull system, we use matrix models and bifurcation theory to investigate population and evolutionary dynamic consequences of adult-on-juvenile cannibalism. We show that in the presence of cannibalism, a population can survive under circumstances of low resource availability which, in the absence of cannibalism, lead to extinction. The evolutionary version of the model shows that cannibalism can be an evolutionarily stable strategy.