Distance Regulation of Hand-Reared Goslings (Anser Indicus) To an Unresponsive Parent: a Study of the Short-Term Dynamics of Attachment
AbstractThis study investigated the ways in which young goslings contribute to the proximity between parent and offspring in geese. It sought to detect the rules governing excursions of hand-reared goslings (Anser indicus) from a stationary and non-responding human 'parent' on a large lawn. Distance to the parent and behaviours (distress calling, feeding and others) were monitored during 149 30-min-sessions of 28 goslings (7-19 days old), most of which were accompanied in some sessions by a sibling. Of two additional experiments, one demonstrated the positive effect of sibling group size on maximum distance from the parent, the other showed that distress calling induced by forced separation from the (human) parent was reduced by the presence of siblings. Excursion analysis revealed that the probability of returning to the parent was independent of time and distance. This allowed rejection of some earlier models of excursion control. Only sudden disturbances in the environment (occurring at random with respect to the start of an excursion), forced separation from the parent, and-similarly-the parent's walking away were found to elicit approach to the parent. The speed of leaving the parent was also independent of time and distance. Thus distance was not limited by an increasing locomotor tendency to return. But rate of distress calling increased with distance. Two causes for the goslings' departures were identified: 1) parental non-signalling (by the "mute" parent), which aroused a tendency "to go home", and 2) hunger combined with the tendency to forage in a fixed direction. Return probability, speed of leaving and distress call rate at any given distance were lower when a gosling was accompanied by a sibling, apparently because the social feedback received from the sibling compensated for the parent's non-signalling. In spite of behavioural tendencies which lead a gosling to potentially unlimited distances from its parents, it will not normally get lost, as it returns whenever alarmed or when the parents walk away, and because goose parents tend to join a gosling distress calling at a distance.