Do Geese Use Path Integration for Walking Home?

Abstract

Whether en route information is used for homing is tested in goslings of different species and adult Domestic Geese. (1) When the geese journeyed out to the starting place with full view, they walked straight home irrespective of the path of arrival. There is no difference in homing orientation after active or passive outward journeys, and no noticeable dependence upon weather conditions. (2) Complete visual shielding during the outward journey prevents homeward orientation , as well as if the cage top and 1/3 of the sides are covered. If only the top of the transportation cage is shielded, and even if the shielding extends over the cage top 30 em horizontally, homeward orientation is as normal. (3) The two-leg experiment clearly shows that the geese compute the home direction during the outward journey. There is also an indication that the mechanism provides the animals with information about their distance from home. Conclusion: So far our results may all be accounted for by the theoretical framework of path integration. It is well known that birds of numerous species are able to return to their nests, burrows or sleeping places from unfamiliar areas. Since it is not known whether the birds use en route or on site information, I shall try to investigate this question. Based on experiments in spiders and gerbils, H. Mittelstaedt has formulated a theory of how en route information may be processed to ensure homing. It postulates that a mechanism of path integration is in operation during the entire journey which allows the animal to return (see Mittelstaedt 1978, Mittelstaedt and Mittelstaedt 1980,1982). The following experiments are designed to test whether it operates in birds. In order to study homing performance on the basis of path integration, the bird has to journey out on a certain path and to return immediately. Since it is extremely hard to train a bird to make such a journey in flight, I had the birds return home on foot. The birds used for the experiments were goslings of the Greylag (Anser anser), the Barnacle Goose (Branta Zeucopsis), and the Bar-Headed Goose (Anser indicus) as well as adult Domestic Geese (Anser anser var. dom.). The following method was used: After hatching in an incubator, the goslings were permanently attended by a human foster mother in a family group of 2-6 goslings. They became imprinted on the foster mother and consequently were tame, a factor which was important for the later experiments. These goose families had well-defined homes. They were made to walk daily within a home range of about 50 x 300 m 1 Max-Planck-Institut flir Verhaltensphysiologie, 0-8131 Seewiesen, FRG Avian Navigation (ed. by Papi/Wallraff)