A: You've obviously let the tenants have a pet and now you're concerned that the pet has caused damages. The tenants are responsible for their pet and any damages the pet might cause. As a landlord you should issue the tenants a letter detailing what your concerns are, what you think the damages are attributable to, and what you think needs to be done and by when. This is sometimes called a 'breach' letter but it really is something that reaches back into ecclesiastical law and stands for the proposition that when somebody is doing you a wrong you must first approach them and tell them to stop. Ecclesiastically, if things don't stop you move up the ladder and go to the offender with a witness in tow. If the actions or offences don't stop with this you go to the village elders, and they go to the offender and explain things to him in a way it may never have been explained to him before. If the elders aren't effective you go off to the local magistrate who holds court and has authority. The appeal from this can involve everybody up to the reigning monarch.
When it is examined, you'll find our present legal system is pretty similar to the ecclesiastical one. You're on the first rung. Take your concerns to the tenants, tell them what's up and that you're looking to them to make things right. Put things in writing. If the tenants don't respond to your satisfaction you move up the ladder, eventually going to arbitration (the local magistrate) with your claim for damages.