Abstract (eng)
In this study, I investigate visual signaling and visual discrimination in greylag geese (Anser anser) during the breeding season, exploring these widespread phenomena aimed at conveying information, influencing receiver responses and recognizing individuals. Previous research demonstrates such signaling across species, revealing a gap in the understanding of visual discrimination, especially in large, socially complex avian groups. Greylag geese, with their intricate social dynamics and potential for individual recognition, provide an ideal model. I also explore sexual dimorphism, while looking at differences in agonistic behavior among these geese. While affiliative and agonistic behaviors in relation to social partners have been observed in various animal groups, it remains unclear if visual discrimination directs these behaviors in greylag geese. Using life-sized photographs of partners, relatives and flock members, I simulate in a series of photo trials, the visual presence of geese and test three hypotheses related to affiliative and agonistic behavior. The results show, geese exhibit differential affiliative and agonistic behaviors in response to photos, appearing to perceive them to some degree as conspecifics. Although no significant differences were found among the three photo trial types (partner, relative and flock member), a subtle pattern hints at distinct responses when presented with a partner's photo, including faster approach times, extended feeding durations, and increased calling and vigilance. Moreover, males show to display heightened vigilance and overall agonistic behaviors as compared to females. This study sheds light on greylag geese's perception of photos and seasonal variations in agonistic behavior, offering potential directions for further research.