Reproductive characteristics of the Yangtze vole (Microtus fortis calamorum) under laboratory feeding conditions.

The reproductive characteristics of a laboratory population of the vole Microtus fortis calamorum were examined. Voles were allowed to breed under laboratory feeding conditions. Over a period of 3 months, 61.82% of the 110 vole pairs examined produced 3 or 4 litters. There were 1-9 voles in each litter and the mean litter size was 4.67±0.28 (mean±SE). Most litters included 3-7 young voles, accounting for 83.62% of all litters. The mean farrowing interval was 25.9 days (range from 19 to 95 days), and the most farrowing intervals were 20-25 days, accounting for 79.9% of the total. When based on litter size, the reproductive index was 6.23, but was 3.42 when based on pup survival. The survival rate of offspring to weaning was 55.03%. The high rate of infanticide that occurred after removal of males from cages indicates that, in the laboratory, both parents need to be present prior to weaning.