Prey conspicuousness can explain apparent prey selectivity

daughters. However, our finding that α α-males sired their daughters' offspring less frequently than non-daughters' offspring remains highly significant when the analysis is restricted to the 34 offspring known to have been born to non­ first time mothers (Fisher's exact p = 0.0003). A third alternative explanation for our findings is that father–daughter matings are not avoided, but when they occur they result in early fetal loss. This phenomenon would result in longer interbirth intervals for the daughters of resident α α-males, compared with other females. However, known interbirth intervals of these two classes of females were indistinguishable: for non-daughters (n = 11) they were 23 months and for daughters (n = 7) 22.5 months (Mann-Whitney U = 32.0, p = 0.55). Thus, the most parsimonious explanation of our results is that father–daughter pairs of white­ faced capuchin monkeys actively avoid mating. Female primates are generally more averse to inbreeding than males [6]. However, because courtship and copulations involving fertile females are rarely observed in this species [7], it cannot yet be determined whether it is the male, the female, or both, that avoid inbreeding. Individuals may avoid inbreeding by recognizing kin through long-term co­ membership in the same group. The Westermarck effect, in which individuals develop sexual aversion to close childhood companions, is well supported in nonhuman primates [6,8]. In our data set, eight offspring that were produced by seven different females (including the single case of father–daughter inbreeding) were nonetheless sired by males who had been co-resident with the female during her infancy. However, white-faced capuchin infants generally spend substantially more time in proximity to the α α-male than to subordinate males, so we cannot rule out a role for social familiarity in producing inbreeding avoidance. Several recent studies also support a role for phenotype matching in mediating recognition of paternal kin in primates [9–11], suggesting that closely related male–female pairs would be predicted to avoid mating even in the absence of close familiarity early in life. (2001). Paternal relatedness and age proximity regulate social relationships among adult female rhesus macaques. To study prey selection, ecologists compare the abundance of food resources with the actual prey spectrum [1,2]; selectivity is inferred when some prey are markedly overrepresented in an animal's diet [3]. However, the capabilities of an animal's sensory systems and the cues provided by potential prey both constrain its foraging behavior and access to food [4–9]. Here …