title: Male chimpanzees' grooming rates vary by female age, parity, and fertility status.
abstract: Copulation preferences in our closest living relative, the chimpanzee, suggest that males prefer older females who have had previous offspring. However, this finding is counter to some behavioral models, which predict that chimpanzee males, as promiscuous breeders with minimal costs to mating, should show little or no preference when choosing mating partners (e.g. should mate indiscriminately). To determine if the preferences indicated by copulations appear in other contexts as well as how they interact, we examined how male chimpanzees' grooming patterns varied amongst females. We found that males' preferences were based on interactions among females' fertility status, age, and parity. First, grooming increased with increasing female parity. We further found an effect of the estrous cycle on grooming; when females were at the lowest point of their cycle, males preferentially groomed parous females at peak reproductive age, but during maximal tumescence, males preferred the oldest multiparous females. Nulliparous females received relatively little grooming regardless of age or fertility. Thus, male chimpanzees apparently chose grooming partners based on both female's experience and fertility, possibly indicating a two-pronged social investment strategy. Male selectivity seems to have evolved to effectively distribute costly social resources in a pattern which may increase their overall reproductive success.
authors: Department of Psychology, Georgia State University, Atlanta. dproctor3@student.gsu.edu
authors: Darby P
authors: DP
authors: Proctor
authors: Susan P
authors: SP
authors: Lambeth
authors: Steven J
authors: SJ
authors: Schapiro
authors: Sarah F
authors: SF
authors: Brosnan
references: Science. 1997 Aug 8;277(5327):828-31
references: 9242614
references: Anim Behav. 2009;77(4):873-885
references: 19498952
references: Nature. 1991 May 2;351(6321):58-60
references: 2027382
references: Mol Ecol. 2001 May;10(5):1279-300
references: 11380884
references: Curr Biol. 2007 Dec 18;17(24):2150-6
references: 18083515
references: Am J Primatol. 2005 Apr;65(4):385-91
references: 15834886
references: Am J Primatol. 2005 Sep;67(1):137-58
references: 16163723
references: Horm Behav. 2004 Aug;46(2):204-15
references: 15256310
references: Am J Phys Anthropol. 2010 Jul;142(3):417-28
references: 20033921
references: Behaviour. 1974;49(3):227-67
references: 4597405
references: J Theor Biol. 1977 Apr 21;65(4):671-98
references: 406485
references: Folia Primatol (Basel). 1979;31(1-2):123-42
references: 488866
references: Heredity (Edinb). 1948 Dec;2(Pt. 3):349-68
references: 18103134
references: PLoS One. 2007 Sep 12;2(9):e886
references: 17849015
references: Curr Biol. 2006 Nov 21;16(22):2234-8
references: 17113387