Shifts in Male Reproductive Tactics over the Life Course in a Polygynandrous Mammal

• Published in: Current biology 2020-05, Vol.30 (9), p.1716-1720.e3
• Main Authors: Silk, Joan B., Städele, Veronika, Roberts, Eila K., Vigilant, Linda, Strum, Shirley C.
• Format: Article
• Language: English
• Subjects: baboon; male reproductive strategy; mating effort; Papio anubis; parenting effort
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2020.02.013

In polygynous and polygynandrous species, there is often intense male-male competition over access to females, high male reproductive skew, and more male investment in mating effort than parenting effort [1]. However, the benefits derived from mating effort and parenting effort may change over the course of males’ lives. In many mammalian species, there is a ∩-shaped relationship between age, condition, and resource holding power as middle-aged males that are in prime physical condition outcompete older males [2–8] and sire more infants [9–12]. Thus, males might derive more benefits from parenting effort than mating effort as they age and their competitive abilities decline [13]. Alternatively, older males may invest more effort in making themselves attractive to females as mates [14]. One way that older males might do so is by developing relationships with females and providing care for their offspring [14, 15]. Savannah baboons provide an excellent opportunity to test these hypotheses. They form stable multi-male, multi-female groups, and males compete for high ranking positions. In yellow and chacma baboons (Papio cynocephalus and P. ursinus), there is a ∩-shaped relationship between male age and dominance rank [12], and high rank enhances paternity success [12, 16]. Lactating female baboons form close ties (“primary associations” hereafter) with particular males [15–20], who support them and their infants in conflicts [15, 19] and buffer their infants from rough handling [20]. Females’ primary associates are often, but not always, the sires of their current infants [16, 20–22]. •The reproductive tactics of male olive baboons change over the life course•There is a ∩-shaped relationship between age, dominance rank, and paternity success•Males often form ties to lactating females whose infants they have sired•Older males are more likely to form these kinds of ties than younger males are Silk et al. document age-related shifts in the reproductive tactics of male olive baboons. There is a ∩-shaped relationship between male age, rank, and paternity success, and some males may form ties to the mothers of their infants. Older males are more likely to form these kinds of ties, reflecting changes in payoffs of mating and parenting effort.