Breeding and reproductive physiology of the desert gerbil, Meriones crassus.

Meriones crassus were bred under laboratory conditions. The mean gestation period was 21.6 days, with a range between 21 and 24 days. The mean litter size was 4.4. Mean litter size varied from 3.4 in October to 5.6 in April. Studies of vaginal smears revealed four phases of the estrous cycle, and the mean length of this cycle was 2--8 days. Most females experienced postpartum estrus, and the majority of postpartum matings were fertile. Mating was not observed during lactation. Implantation was delayed if the female suckled more than two young, and gestation was then prolonged to over 30 days. Young gerbils were weaned by the fourth week and attained adult size within 3 months from birth.