Age Differences in the Response of California Ground Squirrels (Spermophilus beecheyi ) to Avian and Mammalian Predators

The antipredator behavior of juvenile and adult California ground squirrels ( Spermophilus beecheyi ) was videotaped in Experiment 1 to measure the effects of age on assessment of a briefly presented live dog and a model red-tailed hawk ( Buteojamaicensis ) in simulated flight. Adult squirrels treated the hawk as more dangerous than the dog, whereas juvenile squirrels showed less differentiation of the predator types. Juvenile squirrels also perceived the dog as a more immediate danger than adult squirrels did. For Experiment 2, the red-tailed hawk model was compared with models of a nonthreatening turkey vulture ( Cathartes aura ) and crow ( Corvus brachyrhynchos ). Neither age class differentiated the avian models; however, the adult squirrels treated these birds as more threatening than the juvenile squirrels did. Both studies suggest that learning may contribute to predator assessment.