Eggs have species specific receptors on their outer surfaces to which sperm must attach if fertilization is to occur

The  question is; would a drug that binds irreversibly to these receptors be an effective contraceptive in mammals?, the answer is;Yes; because if the receptors are blocked the sperms will not be able to penetrate the zonal pellucida of the egg.  Contraceptives prevents pregnancy by interfering with the normal process of ovulation, fertilization, and implantation.

Because the carnivores keep the herbivore population in check