Fig. 4.

Posterior distributions of reproductive skew values (M^*) in nonhuman mammals as a function of mating system. Points represent posterior means, and lines represent 89% credible regions. The dashed vertical line at M^* = 0 indicates that reproduction is neither positively skewed, nor more equal than would be expected under a random model. Monogamous nonhuman mammals stand out from polygynous nonhuman mammals, in terms of having significantly higher absolute values of male and female reproductive skew, and significantly lower sex differences in skew. Female reproductive skew, in particular, is strongly damped in polygynous species and elevated in monogamous species. Sample sizes: N = 49 nonhuman mammal species (8 monogamous, 41 polygynous).