Nutria (Myocastor coypus) breed in all seasons throughout most of their range, and sexually active individuals are present every month of the year. Reproductive peaks occur in late winter, early summer, and mid-autumn and may be regulated by prevailing weather conditions.
Under optimal conditions, nutria reach sexual maturity at four months of age. Female nutria are polyestrous, and nonpregnant females cycle into estrus (“heat”) every two to four weeks. Estrus is maintained for one to four days in most females. Sexually mature males can breed at any time because sperm is produced throughout the year.
The gestation period for nutria ranges from 130 to 132 days. A postpartum estrus occurs within 48 hours after birth, and most females probably breed again during that time.
Litters average four to five young, with a range of one to 13. Litter sizes are generally smaller during winter, in suboptimal habitats, and for young females. Females often abort or assimilate embryos in response to adverse environmental conditions.
Young are precocial and are born fully furred and active. They weigh approximately 8 ounces (227 g) at birth and can swim and eat vegetation shortly thereafter. Young normally suckle for seven to eight weeks until they are weaned.
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Nutria
