Early testosterone exposure and coping style in geese

With respect to offspring characteristics, mothers are not simply the slaves of genetic recombination, but are able to manipulate their offspring individual behavioural phenotypes to a significant extent via early steroid hormones. This was shown by the research at the Konrad Lorenz Research station in the frame of P12914-BIO. In context with behaviour driving evolutionary change, research usually focussed at factors such as sex, age, life history, reproductive status, nutritive state, genetic background etc., which affect individual interactions with the physical, ecological and social environment. The rest was - heuristically unrevealingly - termed "individual variation". Individuals in populations differ in their behavioural dispositions solely because they are also genetically different. On top of that, it is known since the early 1960ies (work by VomSaal et al.), that steroid hormones during early ontogeny may significantly affect individual behavioural phenotype ("personality"). Recently, it became clear that steroids of maternal origin deposited in egg yolk significantly affect competitiveness and other features of the hatchlings. We tackled this problem experimentally by injecting testosterone into fertilized, but not yet incubated greylag goose and Japanese quail eggs (J. Daisley et al.). The latter species was valuable in supplementing the greylag model, notably because of a much faster life cycle. We wanted to test, whether yolk androgen would have similar effects on offspring behavioural phenotype in nidifugous birds as in birds remaining in the nest up to fledging. Our basic hypothesis was, that from testosterone-enhanced (T+) eggs, individuals would show a sustained shift towards "proactive" (bold, aggressive) style of coping with the challenges of life. Hatchlings from T+ and control eggs were subject to a series of behavioural tests and their corticosterone and testosterone monitored (non-invasively, by EIA from faeces). It showed, that individuals from T+ eggs indeed show a "proactive" behavioural profile as compared to controls. T+ individuals approach novel objects faster, are less shy in novel situations, are less socially dependent and less corticosterone-reactive than controls. In contrast, sexually mature male T+ quail show significantly less pronounced sexual behaviour and higher latencies than controls, but may compensate by a lower-pitched and hence, more attractive call. These seemingly conflicting results may probably be explained by the sequential developmental timing in the ontogenetic differentiation of sexual/non-sexual brain areas. First studies on the role of personality styles in mate choice, partner interactions and reproductive success have been conducted (R. Nowotny et al.), but data analysis is not complete yet. In follow-up projects we intend to focus on such topics and also on the features of offspring from parents of known personality, thereby investigating the genetic and epigenetic components of the genesis of individual behavioural phenotype. Furthermore, we intend to clarify the significance of personality in the context of "social support" (behaviour and hormones). Our contribution in the frame of P12914 probably diminished one of the last large white spots th the heuristic map of ethology, which is "individual variation". We could show that females have the potential to significantly manipulate offspring behavioural phenotype and therefore, have contributed to enhance the predictability of individual behaviour.