Tenant lied on Pet Form with a breed we don’t permit, what now?

[Account Closed]

So, our new tenant signed on for a year lease without a dog at first but with intention to get a dog. We informed them ahead of signing of the breeds we don’t allow. 
Our tenant finally got his new puppy which he is claiming is a Boxer and it is written on the adoption form but with the pictures they sent in, it is clearly a Pit Bull and we don’t allow it. I called the SPCA with the id number and adoption confirmation and found it is truly a Pit Bull. 
Where do I go from here? Give them a timely manner to get out 3-6 months (they have 10 months left on lease), evict right away, or let it stay until end of lease and not sign with them again?

[Russell Brazil]

There's no such breed as simply "pitbull." People who don't own dogs casually call about a dozen different breeds "pitbulls," including some boxer mixes.

[Account Closed]

Ok. Stratfordshire Terrier is the exact breed. I am calling it Pitbull for the sake of this post.

[Lynn McGeein]

@Erika Peketi follow your state and local landlord tenant laws for timing of notices for lease violations. To me, it also depends on your state rules of liability, some open landlord up to easier liability than others for dog bites. If a better state for landlord, maybe see if you can find a different insurance coverage and/or if tenant will pay difference in premium to cover, then require high liability in renter’s policy. In the future, require vet record showing age, breed, and proof of required shots as part of pet addendum, proving not a restricted breed. Also proof of city pet license if required. I don’t allow under 1 year old because puppies cause way too much damage if tenant is not diligent in training, even if they say it will be crate-trained. I will allow a well-trained family dog with restrictions and high liability insurance, no new additions after lease is signed.

[Nathan Gesner]

Quote from @Account Closed:

My process is to serve them with an unauthorized animal violation, fine them $200, and require them to remove the animal within 72 hours and pass an inspection. If they don't do it, the lease will be terminated. Of course, this is all fully disclosed in the lease and my policies.

I also have a policy against animals owned for less than one year (puppies, kittens, or newly adopted animals) because those are the most likely to cause damage.

EDIT: to be more precise, I would not allow the tenant to stay with the animal. Either they get rid of the unauthorized animal, or they all get out.