The present invention provides novel methods for improving the efficiency of artificial activation of unfertilized mammalian oocytes by reducing the intracellular concentration of Zn2+ in the oocyte. The methods of the invention may additionally comprise a preceding step of increasing the intracellular concentration of Ca2+ in the oocyte prior to reduction of the intracellular Zn2+ concentration. The invention further provides unfertilized oocytes activated by the disclosed methods and viable mammalian animals produced from unfertilized oocytes activated by the disclosed methods.