title: Shaking the myth: Body mass, aggression, steroid hormones, and social dominance in wild house mouse.
abstract: In social mammals, the position of a male in the group's hierarchy strongly affects his reproductive success. Since a high social rank is often gained through competition with other males, selection should favour bigger males over smaller ones. We may therefore predict faster growth and/or delayed sexual maturity in dominant males. Likewise, dominants should have higher levels of testosterone, hormone important in many aspects of male dominance. Less obvious is the relationship between dominance and levels of corticosterone but generally higher concentrations are expected in subordinate individuals. We studied body growth, sexual maturation and endocrinal changes in males of two house mouse subspecies, raised in fraternal pairs. Since Mus musculus domesticus is the subspecies which dominates mutual encounters with Mus musculus musculus we predicted higher growth rate, delayed puberty and aggression, and higher testosterone and corticosterone levels in domesticus males compared to musculus. In all comparisons, no differences were found between dominant and subordinate musculus brothers. On the other hand, in M. m. domesticus, dominant males revealed a different growth trajectory and lower corticosterone levels than subordinate males but not delayed puberty and higher testosterone concentrations, thus contradicting our predictions. In inter-subspecific comparisons, musculus males matured earlier but became aggressive at the same time as domesticus males. The musculus testosterone ontogeny suggests that social positions in this subspecies remain unfixed for an extended period and that the increasing levels probably reflect prolonged hierarchy contests. It appears that the ontogeny of behaviour and physiological traits diverge cryptically between the two subspecies.
authors.affiliation: Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Veveří 97, CZ-602 00 Brno, Czech Republic. Electronic address: 328868@mail.muni.cz.
authors.forename: Z
authors.initials: Z
authors.lastname: Hiadlovská
authors.affiliation: Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Veveří 97, CZ-602 00 Brno, Czech Republic.
authors.forename: O
authors.initials: O
authors.lastname: Mikula
authors.affiliation: Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Veveří 97, CZ-602 00 Brno, Czech Republic; Institute of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic.
authors.forename: M
authors.initials: M
authors.lastname: Macholán
authors.affiliation: Institute of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic.
authors.forename: P
authors.initials: P
authors.lastname: Hamplová
authors.affiliation: Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Veveří 97, CZ-602 00 Brno, Czech Republic; Institute of Vertebrate Biology, ASCR, Květná 8, CZ-603 65 Brno, Czech Republic.
authors.forename: B
authors.initials: B
authors.lastname: Vošlajerová Bímová
authors.affiliation: Institute of Vertebrate Biology, ASCR, Květná 8, CZ-603 65 Brno, Czech Republic; Biodiversity Research Group, Department of Zoology, Faculty of Science, Charles University, 13 Viničná 7, CZ-128 44 Prague, Czech Republic.
authors.forename: K
authors.initials: K
authors.lastname: Daniszová
mesh_terms: D000374:Aggression / Q000502:physiology*; D000818:Animals; D015992:Body Mass Index; D003345:Corticosterone / Q000097:blood*; D005260:Female; D008297:Male; D051379:Mice; D012098:Reproduction / Q000502:physiology*; D012930:Social Dominance; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone; D003345:Corticosterone
keywords: Aggression; Corticosterone; Dominance; House mouse; Ontogeny; Testosterone