title: Territorial aggression does not feed back on testosterone in a multiple-brooded songbird species with breeding and non-breeding season territoriality, the European stonechat.
abstract: Testosterone mediates reproductive behaviours in male vertebrates. For example, breeding season territoriality depends on testosterone in many species of birds and in some, territorial interactions feed back on testosterone concentrations. However, the degree to which territorial behaviour and testosterone are associated differs even between species with seemingly similar life histories, especially between species that also defend territories outside the breeding season. Here, we investigate the link between territorial behaviour and testosterone in European stonechats. Previous studies found that territorial aggression in stonechats depends on testosterone in a breeding, but not in a non-breeding context. We investigated whether stonechats show a rise in testosterone during simulated territorial intrusions (STI) during the breeding season. Post-capture testosterone concentrations of males caught after an STI were not higher than those of males caught in a control situation regardless of breeding stage. However, most of the males would have been able to mount a testosterone response because the same individuals that did not increase testosterone during the STI showed a substantial increase in testosterone after injections of gonadotropin-releasing hormone (GnRH). GnRH-induced and post-capture testosterone concentrations were positively correlated and both decreased with successive breeding stages. Further, territory owners with a short latency to attack the decoy expressed higher post-capture testosterone concentrations than males with a longer latency to attack the decoy. Thus, there is no evidence for behavioural feedback on testosterone concentrations during male-male interactions in stonechats. In combination with previous studies our data suggest that testosterone functions as an on/off switch of high intensity territorial aggression during the breeding season in stonechats. The among-species variation in the androgen control of territorial behaviour may be only partly a result of environmental differences. Instead, potential differences in how territoriality evolved in different species may have influenced whether and how a reproductive hormone such as testosterone was co-opted into the mechanistic control of territorial behaviour.
authors.affiliation: Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Eberhard-Gwinner-Straße 6a, D-82319 Seewiesen, Germany; Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, Scotland, UK; Department of Ecology and Ecosystem management, Technische Universität München, D-85354 Freising, Germany. Electronic address: bea.apfelbeck@gmx.de.
authors.forename: Beate
authors.initials: B
authors.lastname: Apfelbeck
authors.affiliation: Am Kuhm 19, D-46325 Borken 1, Germany.
authors.forename: Heiner
authors.initials: H
authors.lastname: Flinks
authors.affiliation: Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Eberhard-Gwinner-Straße 6a, D-82319 Seewiesen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Goymann
mesh_terms: D000374:Aggression / Q000187:drug effects / Q000502:physiology*; D000728:Androgens / Q000097:blood; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D025461:Feedback, Physiological; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D008297:Male; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D020308:Songbirds / Q000097:blood / Q000502:physiology*; D013731:Territoriality; D013739:Testosterone / Q000097:blood*
chemical_list: D000728:Androgens; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone
keywords: Androgen responsiveness; Challenge hypothesis; GnRH; Gonadotropin releasing hormone; Male-male interactions; STI; Simulated territorial intrusion; Territorial behaviour; Testosterone