Testicular Size, Developmental Trajectories, and Male Life History Strategies in Four Baboon Taxa
Sociobiological theory predicts that natural selection via sperm competition will favor greater relative testicular size in adults of polyandrous species than in their monandrous relatives. We have previously shown that, among baboons of the Awash National Park, Ethiopia, “multimale” olive baboons have testes larger relative to total body mass than “one-male unit (OMU)” hamadryas, with most of the difference attributable to a late growth spurt in olives. In this chapter, we use a sample of yellow baboons captured in the Mikumi National Park, Tanzania, and Guinea baboons living in a captive colony to test the prediction that they will resemble olive and hamadryas baboons respectively, in relative, adult testicular size. Like olives, yellow baboons develop large testes in a late growth spurt, while Guineas, like hamadryas, do not. Yellow baboons apparently have relatively smaller testes than olives at all ages, but this effect is probably an artifact of their long-limbed body build and disappears if a measure of trunk volume (rather than total body mass) is used as a proxy of functional body size. Previous work also showed a difference between olive and hamadryas baboons in juvenile testicular ontogeny, explicable in terms of dispersal rather than adult testicular size. Male hamadryas, which breed in their natal group, undergo testicular enlargement earlier than olives, perhaps reflecting general sexual precocity and/or opportunities to sneak copulations while “following” an OMU.
Olive and yellow baboons, which have few mating opportunities before dispersal, have less developed testes as juveniles. Yellow baboons seem to be more extreme than olives in this respect, perhaps reflecting a lower propensity to disperse as juveniles, and thus fewer preadult mating opportunities. The few available data suggest that Guineas tend to resemble hamadryas in testicular ontogeny.
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- Abegglen, J.-J., 1984, On Socialization in Hamadryas Baboons, Associated University Presses, Cranbury, NJ.Google Scholar
- Boese, G. K., 1975, Social behavior and ecological considerations of West African baboons (Papio papio), in: Socioecology and Psychology of Primates, R. H. Tuttle, ed., Mouton, The Hague, pp. 205–230.Google Scholar
- Barton, R. A., 2000, Socioecology of baboons: The interaction of male and female strategies, in: Primate Males: Causes and Consequences of Variation in Group Composition, Kappeler, P. M., ed., Cambridge University Press, New York, PP.97–107.Google Scholar
- Cracraft, J., 1989, Speciation and its ontology: The empirical consequences of alternative species concepts for understanding patterns and processes of differentiation, in: Speciation and Its Consequences, D. Otte, and J. Endler, eds., Sinauer Associates, Sunderland, MA, pp. 28–59.Google Scholar
- Groves, C., 2001, Primate Taxonomy, Smithsonian Institution Press, Washington.Google Scholar
- Harvey, P. H. and Harcourt, A. H., 1984, Sperm competition, testes size and breeding systems in primates, in: Sperm Competition and the Evolution of Animal Mating Systems, Smith, R. L., ed., Academic Press, Orlando, FL, pp. 589–600.Google Scholar
- Henzi, S. P. and Barret, L., 2005, The historical socioecology of savanna baboons (Papio hamadryas) J. Zool., Lond. 265, 215–226.Google Scholar
- Jolly, C. J., 1964, Origins and specialisations of the long-faced cercopithecoidea. Ph.D. Dissertation, University of London.Google Scholar
- Jolly, C. J., 1993, Species, subspecies, and baboon systematics, in: Species, Species Concepts, and Primate Evolution, W. H. Kimbel, and L. B. Martin, eds., Plenum Press, New York, pp. 67–107.Google Scholar
- Kingdon, J., 1997, The Kingdon Field Guide to African Mammals, Academic Press, San Francisco.Google Scholar
- Kinsky, M., 1960, Quantitative Unterschungen an athiopischen Saugetieren: Absolute und relative Gewichte der Hoden athiopischer Affen, Anat. Anzeig. 108:65–82.Google Scholar
- Kummer, H., 1968, Two variations in the social organization of baboons, in: Primates, P. Jay, ed., Holt, Rinehart and Winston, New York, pp. 293–312.Google Scholar
- Kummer, H., 1995, In Quest of the Sacred Baboon, Princeton University Press, Princeton.Google Scholar
- Phillips-Conroy, J. E. and Jolly, C. J., 2004, Dispersal and philopatry in the Awash Baboon Hybrid Zone in Jones, C and Schwibbe, M. (eds) Dispersal and Philopatry in Primates. Primate Report (special Issue) 68:27–52.Google Scholar
- Phillips-Conroy, J. E., Jolly, C. J., Nystrom, P. D., and Hemmalin, H. A., 1992, Migration of male hamadryas baboons into olive baboon groups in the Awash National Park, in: Dispersal and Migration in Nonhuman Primates, E. O. Smith, and D. Sprague, eds., Int. J. Primatol. 13:455–476.Google Scholar
- Pusey, A. E. and Packer, C., 1987, Dispersal and philopatry, in: Primate Societies, B. B. Smuts, D. L. Cheney, R. M. Seyfarth, R. W. Wrangham, and T. T. Struhsaker, eds., University of Chicago Press, Chicago, pp. 259–266.Google Scholar
- Smuts, B. B., 1985, Sex and Friendship in Baboons, Aldine, New York.Google Scholar
- Smuts, B. B., Cheney, D. L., Seyfarth, R. M., Wrangham, R. W., and Struhsaker, T. T., eds., 1987, Primate Societies, University of Chicago Press, Chicago.Google Scholar