A TEST OF THE ACOUSTICAL BATESIAN MIMICRY HYPOTHESIS

John Alcock, Animal Behavior: an Evolutionary Approach, Sixth Edition, Sinauer Associates, 1998

(A) The test apparatus. During acoustical trials, the barrier was lowered and the ground squirrel could no longer see the rattlesnake, but instead heard various sounds coming from the enclosed burrow.

(B) Ground squirrels from the California coast range area (where rattlesnakes are found) spent more time hesitating in the runway leading to the burrow during trials when tapes of rattlesnake rattles (R) and burrowing owl rattles (H) were played in the burrow than when undifferentiated white noise (N) and burrowing owl scream—chatters (S) were played. Ground squirrels from Davis, where rattlesnakes do not live, did not discriminate among the various sounds.