Legal Question in Landlord & Tenant Law in California

The issue that I see is how are the rodents getting into the home? It sounds like there is a gap somewhere in the exterior of the home (unless someone left the door open.) That gap needs to be sealed. You should send notice to your landlord at the address in the lease agreement for notices and give the landlord the opportunity to correct this.

You don't have a right to break a lease just because a rodent gets into the property. Animals don't know your zip code. There are rodents everywhere. In particular, if there is ivy, there are sure to be rats. I used to live in Piedmont, one of the most upscale neighborhoods in the San Francisco Bay Area. We had mice, rats, raccoons and even skunks, that would come out of the neighborhood landscaping and local parks at night. They will always try to get into buildings looking for food. All you can do is keep them out. That is the landlord's obligation as far as sealing the perimeter of the structure so that there are no openings larger than a nickle. Then it is up to you to keep doors closed and anything that would attract them put away (I quickly learned that nothing attracts critters as well as pet food left out beside an open door, for example). It is not your burden to prove you are not responsible, but it doesn't give you a right to break the lease unless you inform the landlord and they do nothing about it.