Seeing evidence tenant has a puppy but no proof

[Ann Downer]

We inherrited tenant 1 month ago with month to month lease that says no pets but $1,000 added security deposit if tenant gets one. No pet when we purchased. Fixing fence in yard we see a small dog crate with towel over top and small rubber bone and also puppy pads left in yard a couple times.  Without having seen the puppy itself, how do we best proceed?

[Karl B.]

In a similar situation someone on BP once said use a dog whistle and the dog will start barking or whining. 

I always thought that was a super clever idea.