The trill of the chase: Eastern chipmunks call to warn kin

The trill vocalization is given by eastern chipmunks (Tamias striatus) when being pursued by a predator. To examine the adaptive significance of this vocalization, we assessed the effects of sex, age, and distance from the burrow on the occurrence of the call. Chipmunks were released either 10 or 100 m from their burrow and chased by an experimenter to simulate a terrestrial predator. We found that adult females trill more often when released 10 m from their burrow (67% of 24 chases) than when released 100 m from their burrow (14% of 21 chases). Adult males, on the other hand, showed no significant difference in their probability of trilling based on the distance from their burrows (45% of 20 chases at 10 m and 55% of 20 chases at 100 m). Adult females trilled more than adult males when released 10 m from their burrow (67% compared with 45%) but less than males when released 100 m from their burrow (14% compared with 55%). Juvenile females only trilled when released 10 m from their burrows (45% of 11 chases), and juvenile males did not trill at all. We attributed sex, age, and location differences in giving the trill vocalization to the effects of kin selection on antipredator behavior.