Koprowski, J. L. 1991. Response of fox squirrels and gray squirrels to a late spring-early summer food shortage. Journal of Mammalogy 72(2): 367-372.

The response of adult and juvenile fox squirrels (Sciurus niger) and gray squirrels (S. carolinensis) to a shortage in their two major May-June foods was monitored and compared to a year of typical food abundance. Squirrels foraged more frequently, but less efficiently, during the year of fruit failure than during the typical year. Juvenile survival of both species was reduced during the year of fruit failure, but adult survival remained high. Juvenile losses occurred during late June when weights of adults and juveniles were lower than in the year of typical fruit abundance. By influencing juvenile survival and body condition of adults, late spring-early summer can be a critical period for populations of tree squirrels.