Hormonal and behavioural symmetries between the sexes in the Northern bald ibis.
Seasonal patterns of fecal androgen and corticosteroid levels were measured in a semi-tame colony of Northern bald ibis (Geronticus eremita) and put in perspective with socio-sexual patterns. Northern bald ibis are monomorphic, monogamous, year-round social colonial breeders. Steroids levels were assessed from the pre-mating until the end of the mating season in the sexes, age groups, and social categories. Male immunoreactive androgen concentrations, determined by enzyme immuno-assay from feces, were relatively low, even during the mating phase, and were close to the female levels. Sexual monomorphy and symmetries in socio-sexual and parental roles may account for this similarity. Males and females responded in a similar way to social challenges from conspecifics, particularly during pair-formation. Singletons showed higher androgen metabolites levels than paired individuals. Corticosterone metabolites were relatively high during periods of social instability in the mating phase and were highest in low-ranking, young individuals. We suggest that the challenge hypothesis may even apply to females in this non-passerine bird.
Sorato
Enrico
E
Konrad Lorenz Forschungsstelle für Ethologie, A-4645 Grunau 11, Austria. klf.gruenau@telecom.at
Kotrschal
Kurt
K
D000818:Animals; D001717:Birds / Q000502:physiology*; D003345:Corticosterone / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005260:Female; D006608:Hierarchy, Social; D008297:Male; D012621:Seasons; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013739:Testosterone / Q000378:metabolism*
D013739:Testosterone; D003345:Corticosterone