title: Early sexual maturity in male hamadryas baboons (Papio hamadryas hamadryas) and its reproductive implications.
abstract: We present data on sexual maturity in young hamadryas baboon males (Papio hamadryas hamadryas) and its reproductive consequences in a large captive baboon colony. Hamadryas baboons live in a multilevel social system, with one-male units (OMUs) as the smallest social entity. Male leaders of OMUs are believed to monopolize matings within their OMUs; hence mating is believed to be polygynous and monandrous. In a captive colony of hamadryas baboons, we found evidence that young males less than 4 years old fathered at least 2.5% of 121 offspring born subsequent to vasectomy of all adult males, and males aged 4-5 years fathered at least 16.5% of the offspring. Additional evidence that these young males are able to sire offspring came from a morphological comparison of sperm from hamadryas males of different ages. The sperm of a 48-month-old hamadryas baboon were morphologically indistinguishable from viable sperm from adult males, whereas sperm from a 45-month-old male showed some aberrations. If successful copulations by adolescent males constitute a regular pattern even in free-ranging hamadryas baboons, a hamadryas male's chances to reproduce would not be limited to his role as an OMU leader as previously assumed, and a male's reproductive career would consist of two phases: the adolescent phase, and the OMU leader male phase.
authors.affiliation: Forschergruppe Kognitive Ethologie, Deutsches Primatenzentrum, D-37077 Göttingen, Germany. dzinner@gwdg.de
authors.forename: Dietmar
authors.initials: D
authors.lastname: Zinner
authors.forename: Ellen
authors.initials: E
authors.lastname: Krebs
authors.forename: Annette
authors.initials: A
authors.lastname: Schrod
authors.forename: Werner
authors.initials: W
authors.lastname: Kaumanns
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D005260:Female; D006608:Hierarchy, Social; D008297:Male; D048529:Papio hamadryas / Q000502:physiology*; D012098:Reproduction; D012726:Sexual Behavior, Animal; D012741:Sexual Maturation / Q000502:physiology*; D012919:Social Behavior