Signaler and receiver ages do not affect responses to Richardson's ground squirrel alarm calls

Alarm calls alert receivers to the presence and/or nature of a predatory threat. Studies of alarm communication in Richardson's ground squirrels (Spermophilus richardsonii) have focussed on juvenile signalers and receivers; however, adult and juvenile receivers may tailor their response to alarm calls based on different underlying signal parameters and attend differentially to alarm calls broadcast by adult versus juvenile signalers. To examine the potential influence of signaler and receiver age on the perception of response urgency, we presented free-living juvenile and adult S. richardsonii with alarm calls produced by juveniles and adults. Behavioral responses of call recipients were videotaped and analyzed to determine the influence of signaler and receiver age-class. No differences in vigilance response after juvenile- and adult-produced calls were detected for either adult or juvenile receivers. At the proximate level, the absence of any detectable difference in the acoustic attributes of juvenile-versus adult-produced calls may account for the lack of differential response. The absence of any age-dependent productional difference also is consistent with the recently advanced notion of young concealing information regarding their age in their alarm signals.