The extra money isn't meant to protect you (the tenant) from anything. It's there to protect the landlord's interest in being able to recoup losses caused by a destructive pet.
If a landlord isn't returning your pet deposit when you move out, it's not a deposit, it's a fee. If they're misrepresenting it as a deposit that will be returned, you might have legal recourse, depending on where you live.
If a landlord isn't returning your pet deposit when you move out, it's not a deposit, it's a fee. If they're misrepresenting it as a deposit that will be returned, you might have legal recourse, depending on where you live.