Because females gestate, birth, feed, and invest more overall resources in each of their offspring, they are more selective with their mates but have greater certainty of being able to reproduce.
Pošto ženke nose, rađaju, hrane i uopšte uzev, ulažu više sredstava u svakog svog potomka, one pažljivije biraju svoje partnere, ali imaju veću sigurnost da će moći da se razmnožavaju.