Male and female laboratory mice (Mus musculus ; Harlan Sprague Dawley) were tested for reactions to snake odors. In the first experiment, mice were presented with untreated paper on the floor of one side of a test tank and snake-scented or control (water misted) paper on the other side. The scented papers were obtained from rough earth snakes (Virginia striatula ), which were fed earthworms, and a rat snake (Elaphe obsoleta ), which ate mice. Male mice exhibited no differences in response to the three conditions. Female mice showed no response to the control or earth snake odor, but they deposited significantly more fecal boli on the side of the tank with the rat snake odor than on the blank side. No significant differences in other behaviors, e.g. ambulation, were detected. In the second experiment, female mice were offered food pellets treated with the shed skin extract of the rat snake or with a solvent alone. Less material was bit off and consumed from the snake-scented pellets. The results of both experiments indicate that female mice detect the odors of rat snakes.