Heart rate modulation by social contexts in greylag geese (Anser anser)

Physical activity is generally considered as most relevant for modulating heart rate (HR). The authors show here that HR is not only modulated by physical activity but even more by social contexts. HR modulation in three free-ranging, socially embedded, male greylag geese fitted with implanted radio-transmitters was investigated. Measured HR ranged from 40 beats per minute (bpm) during rest to a maximum over 400 bpm during takeoff. Almost the same maximum HRs (400 bpm) were reached during social interactions, which however, generally require less bodily action. Mean HR during social interactions (agonistic interactions, vocalizations) was significantly higher than during behaviors with a less obvious social context (e.g., resting, comfort or feeding behavior), but with comparable physical activity involved. The authors also found significant and consistent differences in HR between the three focal individuals, probably because of individual behavioral phenotype. Our results show that social context has a strong modulatory effect on the sympathico-adrenergic activity in a social bird and conclude that particularly the latter may pose considerable energetic costs.