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.

Kinda baboons (Papio kindae) and grayfoot chacma baboons (P. ursinus griseipes) hybridize in the Kafue river valley, Zambia

“…If the chacmas respond in kind, females will not consider the kinda male in the calculus of paternity confusion [Moscovice et al, 2010;Palombit, 2009] and, more significantly, male chacmas may not perceive him as a serious rival in the context of mating. A comparable situation has been observed in captive hamadryas baboons, where fully adult males seem not to prevent reproductively active, juvenile or younger subadult males from copulating with estrous females [Zinner et al, 2006]. An additional factor in the Kafue case may be the male kinda's propensity to actively initiate and maintain an extended grooming bout with a female, even when she is not estrous Weyher, 2010].…”

Variation of hair cortisol concentrations among wild populations of two baboon species (Papio anubis, P. hamadryas) and a population of their natural hybrids

“…Clans include one or more one-male units (OMU), each consisting of a single adult male with several females and their young offspring. An OMU leader male exercises continuous vigilance to defend exclusive access to females of the group, and fathers most, though not all, of its infants (Kummer 1968;Sigg et al 1982;Smith et al 1999;Yamane et al 2003;Zinner et al 2006). Thus, whether a juvenile, an unattached ''bachelor'', or an OMU leader, a male hamadryas baboon mainly interacts in predictable ways with familiar, often related, group-mates.…”

Alternative routes to the leader male role in a multi‐level society: follower vs. solitary male strategies and outcomes in hamadryas baboons

“…Such close association allows the leader to protect his mating access and dependent offspring in an especially male-dominated society [Abegglen, 1984;Kummer, 1968] in which infanticide is known to occur [Swedell & Tesfaye, 2003]. Leader males are not always able to maintain complete reproductive exclusivity, as nonleader males (usually subadult) have been observed to copulate with females [Kummer, 1968;Swedell, 2006] and may be capable of siring offspring [Jolly & Phillips-Conroy, 2003, 2006Zinner et al, 2006], but all evidence to date suggests that leader males sire the majority of infants born into their OMUs [Swedell & Saunders, 2006]. Less coercive-and sometimes less exclusive-versions of female defense polygyny exist in geladas [Dunbar & Dunbar, 1975;Kawai et al, 1983], most guenons [Cords, 2000;Rowell, 1988], many colobine monkeys [Fashing, 2011;Kirkpatrick, 2011], some populations of gorillas [Robbins, 2011], and some populations of other baboon subspecies [Anderson, 1989;Byrne et al, 1987Byrne et al, , 1989Galat-Luong et al, 2006;Hamilton & Bulger, 1993;Smuts, 1985;Swedell, 2011].…”