What do you like doing in your spare time? flock Tricor 145 gloomily pie "This is a form of post-mating sexual selection in which males compete with their sperm inside the female reproductive tract, rather than fighting to gain access to females," Fisher said. "It is associated with having large testes with lots of sperm-producing tissue, and often also long mating times and mate-guarding, and of course promiscuity."