Hormonal correlates of being an innovative greylag goose, -: Anser anser

A number of studies have focused on the spread of foraging innovations within animal populations, but only rarely have individual dispositions of becoming innovative been considered. With two groups of individually marked, hand-reared greylag goslings we investigated hormonal and behavioural correlates related to the individual's ability to perform operant tasks. During individual tests 6 weeks after hatching, goslings were given small food containers covered by lids. In the following winter the sibling groups were tested in a social set-up at a food dispenser, which the geese could activate by pulling a flap. We analysed individual faecal samples collected at 2, 6 and 12 weeks of age, and also after the individual tests, for excreted corticosterone and testosterone metabolites by enzyme immunoassay. During the individual test, 18 of 23 individuals learned to remove the lids. These 18 birds excreted higher faecal corticosterone concentrations than their respective controls 2 weeks after hatching. At the food dispensers, only four males became food producers; all the others scrounged. These four were in the group of 18 that were successful in the individual test and again tended, although not significantly, to have higher faecal corticosterone 2 weeks after hatching than the scroungers. In one of the groups, excreted corticosterone increased and excreted testosterone decreased after the individual test. Goslings successfully removing lids at 6 weeks raised their faecal corticosterone to a significantly greater extent than the unsuccessful individuals. Our results suggest that becoming an innovator may be contingent upon individual coping styles. (C) 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.