When and Why Do They Alarm Call? : Insights From Naturalistic & Automated Monitoring

Abstract

Anti-predator signals are common for animals living in social groups, for they act as a warning to conspecifics. Vocalizations, such as alarm calls, are common signals produced when social animals are faced with potential threats, and the California ground squirrels (Otospermophilus beecheyi) are one such species that produce these calls. As part of our long-term study, we sought to determine the duration, ecological context, and timing of alarm calls produced by ground squirrels. Because they are diurnal, we predicted that the squirrels would produce more alarm calls during the day when they face threats from natural predators (e.g., coyotes, rattlesnakes, birds of prey) and anthropogenic disturbances. To monitor the alarm calls, we combined direct observations and automated passive monitoring system to record acoustic information over the 24-hour cycle. Monitoring equipment was set up in a central location of the study area and recordings were later analyzed using a software system called Raven Pro. Our findings confirmed our hypothesis that ground squirrels mainly call during daylight hours, following an alarm-calling “schedule.” These recordings, along with natural observations, offer novel insights into the temporal patterning of alarm calls, the stimuli triggering alarm call production, and the individual differences in calling propensity.