If your type of pet is excluded, there is no harm in inquiring the reasoning. Perhaps the landlord may just need to be educated. Finally, when there is a definite no-pets stated, you can still inquire. You can explain what pet you have. If the animal is enclosed, describe it's habitat.
Landlords are primarily concerned with property damage and liability to the other tenants.
Some may regard pets as an additional burden to land lording. It doesn't hurt the situation to inquire and explain matters to the tenant. The landlord can react in several ways. There's another situation where they can just give you a 30-day notice to vacate the property. Once you have violated the agreement, you have basically very little alternatives.