Fig. 1. An early springtime view of a site for field studies of California ground squirrel behavior in the foothills of the Sierra Nevada.

Fig. 2. A California ground squirrel standing bipedally. These squirrels commonly adopt such postures in order to monitor mammalian predators, or to look for such predators after hearing another squirrel's "chatter" call.

Fig. 3. A squirrel cautiously approaches a rattlesnake, one of the most important predators of young squirrels. Notice that the squirrel is waving its fluffed tail from side to side, a visual signal used only in the context of dealing with the threat of snakes.

Fig. 4. An infant golden eagle whose parents regularly hunted our ground squirrels. The parents have recently brought their youngster a California ground squirrel to eat (bottom right). Perhaps this squirrel neglected to "whistle," a vocalization typically used by California ground squirrels to deal with avian predators.