Species: Papio hamadryas
Normally, in these posts I try to provide some basic information about the species I’ve picked and provide a few pictures. In this post I would like to do something a little different.
The Animal Diversity Web has an excellent write up of the Hamadryas baboon. I would like, instead, to focus on two aspects of the Animal Diversity Web’s write up:
Puberty in males is a lengthy process, and the timing of different developmental events reveals interesting details about the reproduction of these animals. Testicular development does not closely follow male growth in this species. Testes develop rapidly between the ages of 3.8 and 6 years, reaching full size prior to attainment of full adult body size. In contrast, body mass doubles between the ages of 7 and 8 years, after the testicles are fully developed. This pattern of development may indicate that subadult males, who do not possess OMUs of their own, may yet achieve some “sneak” copulations. Interestingly, the remainder of adult male secondary sexual characteristics, including the silver mane, white cheeks, and pink hindquarters, do not develop until after full adult size is reached. [bold mine – afarensis] These characteristics are thought to function in the maintenance of the OMU, as they are very attractive to the females of the OMU and elicit large amounts of female grooming.
If this reminds you of the post I wrote on red-fronted lemurs congratulate yourself. In that post I talked about how juvenile female red-fronted lemurs maintain a baby pelage until they are old enough to hold their own against other females. In this case, however, males are maintaining juvenile pelage so they can, possibly, poach a few “romantic trysts” with female members of the clan. According to West-Eberhard this kind of strategy is widespread (most noticeably in fish). A second aspect of the Animal diversity write up that I found interesting was this:
The basic unit of social organization is the OMU, or one male unit, in which a central male, the leader, aggressively herds and controls from one to nine females and their offspring. Members of a OMU forage together, travel together, and sleep together. Males typically restrict the social interactions of females and juveniles within their OMU, suppressing aggression between females, and maintaining nearly exclusive reproductive access to the mature females.
This herding behavior has lead to the formation of some interesting hybrid zones where the range of P. hamadryas meets that of P. anubis – the olive baboon. Male olive baboons do not herd their females and, consequently, are not very successful in mating with P. hamadryas females. Male P. hamadryas are quite adept at herding female olive baboons and this is where things get interesting. The male offspring of the male P. hamadryas female P. anubis cross do not seem to have inherited the ability to herd females. This has resulted in a hybrid zone about 20 km wide. Fascinating…