Male home ranges overlap those of several females and males continually compete for access to receptive females. Research using microsatellite analysis of genetic patterns confirmed that the mating system was promiscuous (Stewart et. al., 1999).
Arvicola amphibius undergoes one mating season per year, usually ranging from early spring (April/March) to late summer/early autumn (August/October). During this time water voles can have up to four litters with an average number of four to six young each. The gestation period is short, 21 days, and postpartum estrus and mating usually occurs shortly after birth. Newborn weight is usually 5g, with young opening eyes around 5 days, and becoming weaned 14 to 21 days after birth. Sexual maturity is reached during their first summer, if born early in the season, or in the following mating season (Bazhan et al., 1996; Nowak, 1991). Females may mature as early as 5 weeks of age.
Breeding interval: Water voles can have up to 4 litters in each breeding season.
Breeding season: Breeding occurs from April to October.
Range number of offspring: 2 to 8.
Average number of offspring: 4-6.
Range gestation period: 20 to 22 days.
Average weaning age: 21 days.
Range age at sexual or reproductive maturity (female): 5 (low) weeks.
Range age at sexual or reproductive maturity (male): 5 (low) weeks.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
While males sometimes participate in the raising of the young, the females are the main care givers (Niethammer, 1990). The young are born helpless but rapidly develop and become independent.
Parental Investment: precocial ; male parental care ; female parental care