The changes in the American Shorthair from 1 to 12 months are as follows:
1. 1 month: Weaning and entering the rapid growth period.
2. 2 months: Teeth replacement begins and the tooth replacement period begins.
3. 3 to 4 months: Growth and development enters a new stage and enters the juvenile period.
4. 5 to 7 months: Entering puberty and entering the tooth replacement period.
5. 8 to 10 months: Entering the later stage of development and late adolescence.
6. 11 to 12 months: Entering adulthood.
During this process, American Shorthair cats need nutrition and careful care, regular deworming and immunization, as well as attention to oral health and weight control. At the same time, it will be more vigilant and needs to be prepared for comfort.