Social Support in Greylag Geese (Anser anser)

Support by social allies may reduce stress, increase success in agonistic encounters and ease access to resources. It was so far mainly known from mammals, particularly primates. This study aims at investigating mechanisms and functions of social alliances in Greylag geese (Anser anser). Basically twp types of social support are known: `active social support`, which describes the participation of a social ally in agonistic encounters, and `passive social support` in which a social ally reduces behavioural and physiological stress. Generally, three conditions are considered necessary for the development of social support systems (von Holst, 1998): (a) complex social organization, (b) long-term relationships with bonding partners, and (c) matrilines. Greylag geese mate for life, and offspring stay with their parents for an entire year or even longer and there is evidence for a female-bonded clan system. Therefore, greylags are a promising avian model to study support by social allies. Our main objective is to pinpoint the role of social support as a prime mechanism for individual stress management in freely moving socially intact greylag geese. We are particularly interested whether passive social support, the stress-reducing effect of the mere presence of a social ally, reduces behavioural as well as physiological stress responses. Also, we want to determine the ontogeny of social support in greylag goslings in company of their parents, as well as the distribution of active and passive support provided and received by different social allies, i.e. males, females, and juveniles. We are also interested in the role of family size on social support and thus, in the possible benefits of acceptance of unrelated young (`adoption`). Another question we intend to answer is whether pair partners provide social support not only through active interference, but also through affiliative behaviours, such as close contact after conflict situations. Furthermore, we would like to examine if greylag geese show indeed matrilineal organisation. Lastly, we want to find out whether early social support influences an individual`s quality as a mate and assess the influence of ongoing social support in pairs on life history and future reproductive success. We will use behavioural observations of focal greylag goose families and pairs as well as physiological parameters, such as excreted corticosterone immunoreactive metabolites to measure the `slow` stress response, and heart rate as a determinant of the `fast` stress response. In addition, we plan to investigate whether mesotocin plays a similar part in birds as its mammalian homologue oxytocin, which is known for its positive impact on social bonding. We also would like to quantify systemic prolactin, a hormone often considered as being part of the classical stress response in mammals, as well. In summary, we aim to gain a more comprehensive understanding of individual behaviour-physiology interaction to finally be able to explain at the proximate level why geese and vertebrates in general are social.

Support by social allies may reduce stress, increase success in agonistic encounters and ease access to resources. It was so far mainly known from mammals, particularly primates. This study aims at investigating mechanisms and functions of social alliances in Greylag geese (Anser anser). Basically twp types of social support are known: `active social support`, which describes the participation of a social ally in agonistic encounters, and `passive social support` in which a social ally reduces behavioural and physiological stress. Generally, three conditions are considered necessary for the development of social support systems (von Holst, 1998): (a) complex social organization, (b) long-term relationships with bonding partners, and (c) matrilines. Greylag geese mate for life, and offspring stay with their parents for an entire year or even longer and there is evidence for a female-bonded clan system. Therefore, greylags are a promising avian model to study support by social allies. Our main objective is to pinpoint the role of social support as a prime mechanism for individual stress management in freely moving socially intact greylag geese. We are particularly interested whether passive social support, the stress-reducing effect of the mere presence of a social ally, reduces behavioural as well as physiological stress responses. Also, we want to determine the ontogeny of social support in greylag goslings in company of their parents, as well as the distribution of active and passive support provided and received by different social allies, i.e. males, females, and juveniles. We are also interested in the role of family size on social support and thus, in the possible benefits of acceptance of unrelated young (`adoption`). Another question we intend to answer is whether pair partners provide social support not only through active interference, but also through affiliative behaviours, such as close contact after conflict situations. Furthermore, we would like to examine if greylag geese show indeed matrilineal organisation. Lastly, we want to find out whether early social support influences an individual`s quality as a mate and assess the influence of ongoing social support in pairs on life history and future reproductive success. We will use behavioural observations of focal greylag goose families and pairs as well as physiological parameters, such as excreted corticosterone immunoreactive metabolites to measure the `slow` stress response, and heart rate as a determinant of the `fast` stress response. In addition, we plan to investigate whether mesotocin plays a similar part in birds as its mammalian homologue oxytocin, which is known for its positive impact on social bonding. We also would like to quantify systemic prolactin, a hormone often considered as being part of the classical stress response in mammals, as well. In summary, we aim to gain a more comprehensive understanding of individual behaviour-physiology interaction to finally be able to explain at the proximate level why geese and vertebrates in general are social.