A female has several male mates in this breeding system. Females have greater reproductive variance than males'. Polyandry is uncommon. No primate species is purely polyandrous. Some mating relationships in tamarins are polyandrous but most are monogamous.
Mates provide extensive paternal care in polyandrous relationships.
A male has several female mates. Male reproductive variance is greater than females'. Reciprocity is facilitated by individual recognition and long-term memory. Natural selection favors traits improving reproductive success. Resource-defense polygyny is expected in areas where critical resources are unevenly distributed and clumped.