Reproductive Tactics of Male Savanna Baboons

Abstract

AbstractThe strongly related parameters rank, age and period-of-residence determine which reproductive tactics a savanna baboon male will use primarily. Baboon males go through the following phases with respect to the use of mating tactics, as they are longer in the group and thus grow older and, as a rule, drop in rank: Phase 1. Peripheral, relatively little social contact, low mating success, building up of a social bond with a few females. Phase 2. High mating success, based on individual fighting ability, social bonds mainly with females that are, or will soon be, sexually attractive. Phase 3, variant a. (Males that were very successful in Phase 2). Considerable time devoted to guarding infants conceived in phase 2 and to the mothers of those infants. Mating activity drops sharply compared to Phase 2. Phase 3, variant b. (Males that did not go through a very successful Phase 2). Low mating success through whatever tactic, relatively peripheral. Phase 4. Relatively high mating success, partly through collaboration with other males. Considerable time is invested in the care for potential offspring and their mothers. Phase 5. Diminishing share in the total mating activity in the group. The support for infants is spread over a relatively large class of infants conceived after immigration. Social contact with a large number of females. The data did not show the relation between agonistic rank and mating success predicted by ALTMANN'S priority-of-access model. A modification of the model is presented, which allows for coalition formation among males that are too low in rank to be successful on their own. This model could not fully explain, however, the exceptional success of some middle ranking males. The theory of Coalition games can give insight in the processes that lead to distributions of mating success that depart from the modified priority-of-acces model. The lack of agreement between the data and the original priority-of-access model cannot be explained by higher selectivity of the high ranking males. The only qualitative parameter of consorts obtained, according to which high ranking males had an advantage, is the time of the day on which mating activity takes place. This is a direct result of the way in which males obtain their consorts. Consorts are often formed in the sleeping trees during the night or in the early morning. In that situation single, strong males have an advantage in conflicts against coalitions of lower ranking males. Lower ranking males have a relative advantage later in the day, when conflicts are fought out on the ground.