Meeting Abstract
Acoustic signals are an important way in which animals communicate with another and vocalizations may convey much information about the state of the signaler to receivers such as their sex, age, or individual identity. Less is known about the ability of acoustic signals to communicate labile information to receivers, such as short-term changes in hormone levels. We examined the influence of changes in physiological stress state on the acoustic structure of the territorial vocalizations of wild North American red squirrels (Tamiasciurus hudsonicus) known as rattles. We assessed the effects of physiological stress state on the acoustic structure of rattles by applying an acute stressor (trapping and handling the squirrels) and by treating squirrels with exogenous glucocorticoids (GCs). We characterized the acoustic structure of rattles emitted by these squirrels by measuring rattle duration, mean frequency, and entropy. Our results provide mixed evidence that rattles show a “stress signature”. Squirrels experiencing an acute stressor produced rattles that were dramatically different from those recorded from squirrels at baseline conditions. However, the same shifts in rattle acoustic structure were not observed when squirrels were treated with GCs compared to those fed supplemental food or those that were unmanipulated. Our results indicate that acute stress impacts the acoustic structure of vocalizations but changes in circulating GC levels are not solely responsible for such changes.
