From Scientific American:
Nut-obsessed squirrels scurry around collecting and secreting away food for the future. The amount of acorns they find, though, is not what determines how many baby squirrels there will be in the spring. Instead, squirrels predict how abundant their food supply will be the following year and coordinate a second litter to be born during times of bountiful harvests, says a new study.
Some trees, including those with seeds favored by red squirrels, have years of very high seed yields, followed by years of lower seed production, creating what Stan Boutin, a biologist at the University of Alberta, calls a “swamp and starve” strategy. Usually, the size of a predator population depends on how much food is available. When resources are plentiful, they reproduce more. The problem is that the food supply may dwindle by the time their young are born.
More here.