Pregnancy concurrent with lactation in the Mongolian gerbil (Meriones unguiculatus)

The reproductive performance of Mongolian gerbils mated post partum and allowed to nurse 1-12 young was recorded. More than 70% of the post-parturient females mated, the majority on Day 1; the incidence of mating was unaffected by nursing. However, both fertility and fecundity declined as the number of young nursed increased. Smaller litters were associated with longer gestations.