Male takeover , infanticide , and female countertactics 5 in white - headed leaf monkeys ( Trachypithecus leucocephalus )

9 10 Abstract Infanticide by males is common in mammalian 11 species such as primates in which lactation lasts much 12 longer than gestation. It frequently occurs in one-male 13 groups following male takeovers and is likely a male 14 reproductive strategy. Reported female countertactics 15 include abrupt weaning of infants, dispersal, or paternity 16 confusion. Here, we estimated costs of female counter17 tactics in terms of weaning ages and interbirth intervals. 18 We observed a population of white-headed leaf monkeys 19 (Trachypithecus leucocephalus) in Nongguan Nature Re20 serve, China (1995–2006) mainly composed of one-male 21 groups. Takeovers (N=11) coincided with the peak concep22 tion period. Detailed data are presented for five takeovers 23 (34 females, 29 infants, and 47 group-years) leading to six 24 infant disappearances (42.9% of infant mortality). All 25 presumed infanticides were in accordance with the sexual 26 selection hypothesis. Following a takeover, females without 27 infants or with old infants stayed with the new males, 28 incurring no or low costs (via abrupt weaning). Females with 29 young infants dispersing with the old males also experienced 30 low costs. High costs (due to infant loss) were incurred by 31 pregnant females and those with young infants who stayed 32 with the new males indicating that paternity was not 33 confused. Costs in terms of long interbirth intervals were 34 also high for females leaving with the old males to later join 35 the new males, despite infant survival. Female countertactics 36 reflected female philopatry mediated by infant age. 37 Presumably due to the seasonal timing of takeovers, 38 most countertactics seemed successful given that 32.3% 39 of females apparently incurred no costs and 41.2% 40 incurred only low costs.