Numerical method for estimating coefficients of relationship in a langur troop

The average coefficient of relationship ( r ij) among the members of a social group is expected to influence the evolution of any trait that affects the average fitness of group members other than the bearer of the trait. It is usually impossible to write a general expression for r ij , because it depends on a large number of variables, including the means and variances of group size, age-specific reproduction and mortality for males and females (lx and mx schedules), and migration rates (both into and out of the group, for males and females, by age), as well as other features of the mating system such as patterns of assortative or disassortative mating. Fortunately, tractable numerical methods are easy to devise for some special cases. This appendix describes a method that was used to estimate rij among the adult females of a hypothetical troop modeled after the langurs of the Mount Abu region.