Pre- and postnatal environmental effects as potential sources of variation in neophobic behaviour in canaries
Faculty of Sciences. Biology
Behaviour : an international journal of comparative ethology. - Leiden, 1948, currens
, p. 849-867
University of Antwerp
Neophobia, the fear of new objects or stimuli, has been shown to be affected by both maternal effects and the environmental conditions experienced during development. However, both pathways have so far only been studied in isolation, even though maternal effects are known to have significant effects on early development. Thus, maternal yolk hormones an important mediator of maternal effects may affect neophobia both through direct effects on neophobic behaviour and/or by affecting the early development. Both pathways may even act in concert. We measured the neophobic response and habituation to novel food, as well as the response to a novel object in 8-months-old canaries (Serinus canaria). All birds hatched from eggs with elevated yolk testosterone levels or control-treated eggs, and grew up in distinct experimentally-manipulated positions within the sibling hierarchy, which allowed us to test whether and how the effects of prenatally elevated yolk testosterone levels on neophobic behaviour vary with the environmental conditions experienced post-hatch. Neither the experimentally-manipulated yolk testosterone levels nor the position within the sibling hierarchy had a direct effect on neophobic behaviour. The elevation of the yolk testosterone levels modulated the neophobic behaviour and the habituation to novel situations of juvenile canaries only in interplay with the experimentally manipulated position in the sibling hierarchy and offspring sex. The strongest increase of neophobic behaviour was observed in individuals that hatched from eggs with elevated yolk testosterone content while growing up in a superior position in the sibling hierarchy and in males. However, these effects varied with the focal explanatory variable. Based on our results and a review of the literature, we conclude that neither prenatal maternal nor early environmental effects post-hatching form the main source of variation of neophobia in itself, but that the effects observed as well as the inconsistency thereof can best be explained by the interaction of different partly unknown pathways.