Table 3.

Female counterstrategies

Female counterstrategy	Evidence for	Evidence against	Data needed/alternatives	Support Sumatra	Support Borneo
Coalition formation	None	Predominately solitary species (for review, see Delgado and van Schaik 2000)	N/A	−	−
Aggression by mothers against stranger males	None	No males attack on infants reported so lack of aggression is fitting	N/A	−	−
Avoidance of potentially infanticidal conspecifics	Not available	Female inability to avoid sexual coercions and forced copulations by stranger males (Fox 2002) indicates similar inability to avoid infanticide	Calculations of expected encounter rates needed to test female avoidance of specific males	?	?
Female promiscuity	Multi-male mating argued as paternity confusion; female proceptivity during pregnancy (Stumpf et al. 2008)	No significant differences in female proceptivity toward unflanged males in conceptive and nonconceptive periods; female resistance toward unflanged males declines significantly outside nonconceptive periods; males solicit all copulations during POP (Stumpf et al. 2008)	Multi-male mating as convenience polyandry/avoidance of sexual harassment. Determine percent of resident males with whom females mate between weaning and conception; determine probability of nursing female encountering a nonresident male with whom she has not mated	+/−	+/−
Territoriality	None	Males and female have highly overlapping home ranges (Galdikas 1988; Singleton and van Schaik 2002; Knott et al. 2008)	N/A	−	−

Evidence for and against common mammalian female counterstrategies to infanticide (for review, see Ebensperger 1998) exhibited by orangutans. Conclusion for presence or absence of counterstrategy indicated as positive, negative, or unknown (+/−/?) for Sumatran and Bornean orangutans