Lutra lutra has a continuous breeding cycle and female otters have a continuous estrus cycle. Mating can take place either in water or on land. The main mating season is from February to March and July. Gestation lasts 60 to 70 days and weaning occurs at 3 months. Each female river otter usually gives birth to 2 or 3 cubs which are 99 to 122gm at birth. The cubs' eyes open after one month and they begin to leave the nest after two months. The young stay with their mothers for up to 14 months and reach sexual maturity after 2 or 3 years. (Heggberget 1994, Grzimek 1990)
Average birth mass: 110.5 g.
Average gestation period: 61 days.
Average number of offspring: 2.
Average age at sexual or reproductive maturity (male)
Sex: male: 548 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 548 days.