Active and passive social support in families of greylag geese (Anser anser)

Abstract

In general, support by social allies may reduce stress, increase success in agonistic encounters and ease access to resources. Social support was mainly known from mammals, particularly primates, and has been studied in birds only recently. Basically two types are known: (i) 'active social support', which describes the participation of a social ally in agonistic encounters, and (ii) 'passive social support' in which the mere presence of a social ally reduces behavioural and physiological stress responses. In greylag geese (Anser anser) offspring stay with their parents for an entire year or even longer and therefore are a candidate avian model to study support by social allies. We investigated the effects of active and passive social support in ten families (ten males, ten females, 33 juveniles) in a free-roaming, semi-tame flock of greylag geese. Focal individuals were observed during three time periods: (i) re-establishment of the flock in the fall, (ii) stable winter flock, and (iii) disintegration of the flock and break-up of family bonds. We recorded all agonistic interactions of the members of one focal family during morning feedings for two consecutive days: a control day, in which food was distributed widely, and a social density stress situation, in which the same amount of food was spread over a much smaller area. In addition, we collected faeces of all individuals within this family for three hours from the beginning of the feeding situation for determining excreted corticosterone immuno-reactive metabolites by enzyme immuno assay. We found that the small families, i.e. pairs with one or two accompanying young, were involved in more agonistic interactions, mainly through the lack of active social support, as compared to large families in the same situation. Members of greylag goose families lost agonistic encounters significantly less often when actively supported. In addition, the excretion of corticosterone metabolites was significantly decreased in large families during a social density stress situation, probably as an effect of passive social support. Via such a socially induced decrease in hormonal stress response during challenging situations, an individual's long term energy management may benefit.

Coalitions in theory and reality: a review of pertinent variables and processes

“…Coalitions for competition against conspecifics from other groups (hereafter 'group-wide coalitions') occur when the opponents belong to different social groups (or family units, e.g., Scheiber et al, 2005), whereas within-group coalitions occur when two or more members of the same group compete against at least one other 'ingroup' member. Group-wide coalitions can be offensive if individuals join forces to oust incumbent male(s) and take over a group (e.g., Pope, 1990;Rood, 1990;Packer et al, 1991;Waser et al, 1994;Ostner & Kappeler, 2004), or to conduct a lethal attack on members of a neighbouring group (reviewed by Wrangham, 1999;Wilson et al, 2014).…”

Within-brood social status and consequences for winter hierarchies amongst Mallard Anas platyrhynchos ducklings

“…However, in this study, only four individuals from each brood were followed into winter. These four may have had strong associations with siblings and profited from their active or passive social support in aggressive encounters during the duckling period (Scheiber et al 2005). If these siblings were more subordinate and afterwards not present in the winter group, we cannot exclude the possibility that the re-arrangement of the social relationships among siblings between the duckling period and the early-winter phase was related to the change in the sibling-group composition between these two periods.…”

“…Brood effects during winter could not be due to passive or active social support by the mother (Weiß and Kotrschal 2004) because mothers were not present during the second part of the experiment. Brood effects might be due to social support by siblings: dominant males may actively interfere in interactions involving their siblings or may tolerate the proximity of siblings more than that of unrelated individuals, having indirect consequences on their siblings' social rank (Scheiber et al 2005). Our present data do not allow the testing of this hypothesis.…”

A longitudinal study of dominance and aggression in greylag geese (Anser anser)

“…For intraspecific interactions, it is well documented that males are more aggressive and more dominant than females (e.g., Boyd 1953;Black and Owen 1987;Poisbleau et al 2006) and that families dominate pairs in aggressive encounters, whereas pairs tend to win against single individuals (e.g., Boyd 1953;Raveling 1970;Lamprecht 1986;Gregoire and Ankney 1990;Kotrschal et al 1993;Poisbleau et al 2006). Agonistic interactions within pairs or families are extremely rare (Boyd 1953;Scheiber et al 2009a), and members of a social unit actively and passively support each other in conflicts with other flock members (Weiß and Kotrschal 2004;Scheiber et al 2005Scheiber et al , 2009aScheiber et al , 2009b. Several studies further showed that family size affected rates of aggression as well as dominance rank (whitefronted geese, A. albifrons, Boyd 1953; snow geese, A. caerulescens, Gregoire and Ankney 1990; barnacle geese, Branta leucopsis, Loonen et al 1999), but such effects were absent in other studies (bar-headed geese, A. indicus, Lamprecht 1986; brent geese, B. bernicla, Poisbleau et al 2006;snow geese, Mulder et al 1995).…”