Pet owners are encouraged to maintain chinchillas in single-sex groups to provide companionship but avoid producing large numbers of offspring. Male chinchillas must be grouped before weaning or neutered to prevent fighting. When breeding, potential mates should be introduced before the female enters estrus, the time during which she is receptive to mating, to reduce fighting and increase compatibility. Males need a refuge box to escape potentially aggressive nonestrous females. Repeated aggression can teach the male to avoid females, making him an unsatisfactory breeder.
Pregnancies last for about 111 days. Pregnant females should be handled gently. As the female chinchilla approaches the time to give birth, she may become less active, lose her appetite, and become aggressive toward previously compatible cage mates. Chinchillas do not typically build nests as the time to give birth approaches, but a nesting box may help reduce the number of newborn deaths caused by drafts or cold stress. Kits with dangerously low body temperatures should be warmed and revived quickly to prevent death. Chinchillas have up to 4 kits per litter (2 is usual) and may have 1 to 3 litters per year. The kits are born with fur and open eyes and should be able to walk within an hour of birth. Weaning occurs at 6 to 8 weeks of age.