Chinchillas tend not to get along well when housed together, with the female being the more aggressive gender. Breeders and pelters commonly set up polygamous colonies with one male having access to five or so females maintained in separate cages. The male has a tunnel along the back of the females cages which enables him to enter any cage at will. The females cannot pass through the tunnel because they are fitted with light-weight collars that are just a little wider than the cage opening. May. Estrous cycles vary from 30 to 50 days.
Many female chinchillas have irregular cycles.
The female chinchilla can be quite aggressive towards the male. For this reason, males are given the opportunity to escape from the female's cage. This is accomplished by placing a collar around the female's neck and having a small exit hole that the male can climb through, but the female wearing a collar cannot. In cases such as this, changing of the male may raise the conception rate. The gestation period is 111 days on the average, with a range of 105-115 days.