Breeding and reproduction of fifteen wild rodents maintained as laboratory colonies.

Data on reproduction and production were presented for laboratory colonies of Microtus pennsylvanicus tananaensis, M oeconomus macfarlani, M o operarius, M mirurus, M abbreviatus, Lemmus lemmus, L sibiricus trimucronatus, Dicrostonyx stevensoni, Clethrionomys rutilus, Peromyscus maniculatus borealis, P m bairdii, Baiomys taylori, Calomys ducilla, C callosus, Acomys cahirinus. Litter size varied from 2.0 in A cahirinus to 5.5 in C callosus. Infant (neonatal) and juvenile losses through the end of the first month ranged from 9% in C callosus to 45% in M o operarius. Young successfully weaned per female ranged from 3.4 in L sibericus to 15.2 in P m bairdii. The number of young weaned per female per month, which may be the most useful measure of production, ranged from 0.6 in A cahirinus to 2.6 in C ducilla. The most common 21-da interval between litters confirms postpartum estrus and mating, and a 21-da gestation in most cricetids.