Digestibility in greylag geese (Anser anser): the role of social context

1Core facility KLF for Behaviour and Cognition, University of Vienna, Fischerau 11, 4645 Grünau im Almtal, AUSTRIA; didone.frigerio@univie.ac.at 2Department of Behavioural Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, AUSTRIA 3Department for Agro-Food, Environmental and Animal Science, University of Udine, Via delle Scienze 206, 3310 Udine, ITALY Social context is known to modulate physiology, behaviour, fertility and immune system of group living animals. Furthermore, individuals‟ nutritional strategies may affect their performance and impact their social interactions. In the present study we discuss the results of a pilot study conducted on N = 38 individuals of the semi-tame, long-term monitored and individually marked flock of Greylag geese (Anser anser) at the Konrad Lorenz Research Station in Upper Austria. Focal birds belonged to different social categories within the flock, i.e. paired with and without offspring, single and juveniles (five males and three to five females per category). The animals are well habituated to the close presence of humans and are used to get fed twice a day on the meadow in front of the Research Station. During 9 consecutive days in winter 2017, when the snow pack was closed, after standardization of the provided food, a total number of 184 individual droppings were collected from the focal individuals (mean = 4,8; SD = 0,4). Samples were analysed by determining the apparent digestibility of total organic matter. Preliminary results show similarities between males and females but hint at differences depending on the social category with parental individuals showing higher digestive capability than unpaired individuals or paired without offspring. We discuss our findings with respect to the complex relationships between social status, physiology and the capacity of digesting food, extracting nutrients and improving fitness