Effect of Male Competition on Male‐Female Relationships in Bi‐male Groups of Mountain Gorillas

In gorillas ( Gorilla gorilla beringei ), male reproductive competition is manifested during inter‐group encounters through displays and contact aggression with opposing males and through attempts to control the movement of females between groups. This paper documents the effect of within‐group male reproductive competition on male‐female relationships. In one‐male groups, females are known to take the initiative in the maintenance of their relationships with males. In two‐male units, because males face within‐group reproductive competition, one can expect a reversed pattern of responsibility for proximity maintenance. Three measures were used to assess responsibility for proximity maintenance: Hinde's index of proximity: the proportion of ‘follows’ and ‘neighing’. The proportion of follows is the number of follows in relation to the number of departures within each dyad. Neighing is a vocalization emitted by males towards departing females. It is used as a measure of males' motivation to negotiate proximity with females. The data come from focal observations on the silverbacks and ad libitum data collected over 8 months (380 h in 1989) at the Karisoke Research Center. Results indicate that within‐group reproductive competition in itself does not lead to a reversed pattern of responsibility in proximity maintenance between males and females, but that the stability of the dominance relationship between the males, and the quality of the relationship between males and females, might have a role to play as well. Results on the neighing vocalization suggest that males are eager to negotiate proximity with cycling females rather than with lactating or pregnant females.