I investigated whether free-living adult golden-mantled ground squirrels (Spermophilus lateralis) could learn to associate a novel sound with the appearance of a predator. Using a classical conditioning protocol, I presented adult squirrels with a novel tone followed by the appearance of a model hawk. After repeated trials, I again measured the squirrels’ behavioral responses to the tone and compared them with their pretraining responses. Individuals that experienced the tone paired with the hawk responded with antipredator behavior of longer duration after pairing than before and these responses were indistinguishable from responses to natural, conspecific alarm calls. By examining the process, rather than simply the pattern, of call recognition ontogeny, this study provides new evidence for a mechanism by which animals can develop the ability to respond to both conspecific and heterospecific calls.