Effects of different doses of tannins on the reproduction of Brandt’s vole (A) The effect of embryo number and litter size of Brandt’s vole treated with different doses of tannin. (B) Female-male ratio of offspring of Brandt’s voles treated with different doses of tannic acid (n=13). Data are expressed as the mean ± sem. * P < 0.05, **P < 0.01.