Juvenile Greylag Geese (Anser anser) Discriminate between Individual Siblings

Social species that maintain individualised relationships with certain others despite continuous changes in age, reproductive status and dominance rank between group members ought to be capable of individual recognition. Tests of “true” individual recognition, where an individual recognises unique features of another, are rare, however. Often kinship and/or familiarity suffice to explain dyadic interactions. The complex relationships within a greylag goose flock suggest that they should be able to recognise individuals irrespective of familiarity or kinship. We tested whether six-week-old hand-raised greylags can discriminate between two of their siblings. We developed a new experimental protocol, in which geese were trained to associate social siblings with geometrical symbols. Subsequently, focals were presented with two geometrical symbols in the presence of a sibling associated with one of the symbols. Significant choice of the geometrical symbol associated with the target present indicated that focals were able to distinguish between individual targets. Greylag goslings successfully learned this association-discrimination task, regardless of genetic relatedness or sex of the sibling targets. Social relationships within a goose flock thus may indeed be based on recognition of unique features of individual conspecifics

Statistical results of the generalized linear mixed model (GLMM) to determine possible influences on the performance in the recognition task.

<p>The binomial response variable was correct/wrong choice in the ultimate 32 trials of the 15 focal individuals. For the full model, results of all tested fixed terms are given. For the final model, results of terms that remained in the final model are given in bold, and results of excluded terms when individually re-entered into the final model are given in italics.</p

Performance of the 15 focal individuals on the penultimate and ultimate days when goslings passed the task, or of the 40^th and 41^st days of the individuals that did not pass (DNP) the task in the allotted time.

<p>Session marked in bold indicate performance above chance (Binomial tests P<0.05).</p

Percentage of correct and wrong choices of all 15 focal individuals on the penultimate and ultimate day of the recognition task.

<p>81.25% and above marks a performance above chance (dotted line). Asterisks mark significant differences: <i>p<0.001</i>.</p

Detailed information of the 15 focal individuals, which participated in the sibling recognition experiment as well as the randomly chosen sibling targets.

<p>Sibling targets marked in bold represent targets genetically related to one another.</p