title: Up to the challenge? Hormonal and behavioral responses of free-ranging male Cassin's sparrows, Peucaea cassinii, to conspecific song playback.
abstract: The Challenge Hypothesis postulates that male vertebrates can respond to social challenges, such as simulated territorial intrusions, by rapidly increasing their concentrations of plasma androgens, such as testosterone (T). This increase may facilitate the expression of aggressive behavior and lead to persistence of this behavior even after withdrawal of the challenge, thus potentially promoting territoriality and the probability of winning future challenges. The scope of the Challenge Hypothesis was tested by exposing free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback (SPB) at the beginning of the vernal nesting season. Exposure to SPB stimulated aggressive behavior but did not influence plasma T. Furthermore, plasma T did not correlate with the duration of exposure to SPB, and the behavioral response to SPB did not differ in males that were challenged a second time shortly after the first challenge. As birds were investigated at a stage of their reproductive cycle when plasma T is presumably seasonally high due to photostimulation, the lack of hormonal response to SPB may have been due to the hypothalamus-pituitary-gonadal axis secreting hormones at maximum rates. This was not the case, however, because administration of gonadotropin-releasing hormone I rapidly stimulated the secretion of luteinizing hormone (LH) and T, and treatment with ovine LH rapidly stimulated T secretion.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA. deviche@asu.edu
authors.forename: Pierre
authors.initials: P
authors.lastname: Deviche
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Sharp
authors.forename: Alistair
authors.initials: A
authors.lastname: Dawson
authors.forename: John
authors.initials: J
authors.lastname: Sabo
authors.forename: Bobby
authors.initials: B
authors.lastname: Fokidis
authors.forename: Scott
authors.initials: S
authors.lastname: Davies
authors.forename: Lori
authors.initials: L
authors.lastname: Hurley
mesh_terms: D000465:Algorithms; D000818:Animals; D000835:Animals, Wild / Q000097:blood / Q000378:metabolism / Q000502:physiology; D001522:Behavior, Animal / Q000502:physiology*; D005426:Flight, Animal / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000097:blood / Q000378:metabolism; D006702:Homing Behavior / Q000502:physiology; D006728:Hormones / Q000097:blood / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism; D008297:Male; D012726:Sexual Behavior, Animal / Q000502:physiology; D046370:Sparrows / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D013731:Territoriality; D013739:Testosterone / Q000097:blood / Q000378:metabolism; D014828:Vocalization, Animal / Q000502:physiology*
chemical_list: D006728:Hormones; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone