Adult beavers mate with their partners, though partner replacement appears to be common. A beaver that loses its partner will wait for another one to come by. Females may have their first estrus cycle of the season in late December and peak in mid-January. They may enter estrus two to four times per season; each cycle lasts 12–24 hours. Mating typically takes place in the water but may also occur in the lodge and lasts 30 seconds to three minutes. Gestation lasts 104–111 days, up to four young or kits being born. Newborn beavers are precocial and fully furred and can open their eyes within a few days. Their mother is the primary caretaker, while their father maintains the territory. Older siblings from a previous litter also play a role.