title: Androgen correlates of male reproductive effort in wild male long-tailed macaques (Macaca fascicularis): A multi-level test of the challenge hypothesis.
abstract: The challenge hypothesis (Wingfield et al., 1990) has been broadly utilised as a conceptual framework to study male androgen correlates of reproductive challenges in mammals. These studies mainly assessed male androgen responsiveness to a general degree of challenge over extended periods of time. Short term co-variation between the socio-sexual challenging context and androgen levels remains, however, largely understudied. We thus aim at providing a multi-level test of the challenge hypothesis by investigating the inter- and intra-individual variations in faecal androgen excretion associated to 1) breeding seasonality, 2) dominance rank, 3) mate-guarding activity and 4) value of the guarded female. We studied long-tailed macaques, a species in which males engage in highly challenging monopolisation of females over discreet periods of time. This particularity allows testing specifically the predicted increase from level B to level C in the challenge hypothesis. The study was carried out during two reproductive seasons on three groups of wild long-tailed macaques. We combined behavioural observations and non-invasive measurements of faecal androgen metabolite (fAM) levels. We found that, as predicted by the challenge hypothesis, male long-tailed macaques respond not only to seasonal but also to short term reproductive challenges by adapting their androgen levels. First, males exhibited a seasonal rise in fAM levels during the mating period which may be triggered by fruit availability as shown by our phenological data. Second, males had increased androgen levels when mate-guarding females and, across mate-guarding periods, males had higher fAM levels when monopolising high-ranking parous females than when monopolising low-ranking ones. Finally, high-ranking males had higher fAM levels than low-ranking males year round. Our study confirms that, in species with a high degree of female monopolisability, androgen may be an important physiological fitness enhancing tool for males by increasing female monopolisation efficiency (in particular with highly valuable females) and helping males to respond to rank take-over challenges.
authors.affiliation: Jr. Research Group Primate Sexual Selection, German Primate Centre, Kellnerweg 4, 37077 Göttingen, Germany; Courant Research Centre Evolution of Social Behaviour, Georg-August University, Göttingen, Kellnerweg 6, Germany. Electronic address: cedric_girard@eva.mpg.de.
authors.forename: Cédric
authors.initials: C
authors.lastname: Girard-Buttoz
authors.affiliation: Endocrinology Laboratory, German Primate Centre, Kellnerweg 4, 37077 Göttingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Heistermann
authors.affiliation: Faculty of Veterinary Medicine, Syiah Kuala University, Banda Aceh, Indonesia.
authors.forename: Erdiansyah
authors.initials: E
authors.lastname: Rahmi
authors.affiliation: Faculty of Veterinary Medicine, Bogor Agricultural University, Bogor, Indonesia.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Agil
authors.affiliation: Faculty of Veterinary Medicine, Bogor Agricultural University, Bogor, Indonesia.
authors.forename: Panji
authors.initials: P
authors.lastname: Ahmad Fauzan
authors.affiliation: Jr. Research Group Primate Sexual Selection, German Primate Centre, Kellnerweg 4, 37077 Göttingen, Germany; Courant Research Centre Evolution of Social Behaviour, Georg-August University, Göttingen, Kellnerweg 6, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Engelhardt
mesh_terms: D000374:Aggression / Q000502:physiology; D000728:Androgens / Q000032:analysis*; D000818:Animals; D005243:Feces / Q000737:chemistry; D005260:Female; D008252:Macaca fascicularis; D008297:Male; D012621:Seasons; D012726:Sexual Behavior, Animal / Q000502:physiology*; D012930:Social Dominance
chemical_list: D000728:Androgens
keywords: Challenge hypothesis; Dominance rank; Female reproductive value; Male–male competition; Mammals; Mate-guarding