I have to educate me on that whole search warrent thing abit better, florida sure does have some cool laws that protects the good citizens over the criminal elemnt.
Ok here is the short version.. To investigate a crime without a warrant you can enter upon property that is not gated or fenced to make contact. To search the premises you need a warrant, with the exception of exigenet (spelling) circumstances, or to conduct an officer safety sweep (which really wouldnt be relevant in this case. Now if you can see the crime from the roadway or place you can legally be, you dont need the warrant to seize evidence (plain sight doctrine).
If your yard is fenced and animal control (aspca) what ever they are called in your county comes knocking on your door tell them pound sand and time to leave. Unless they have a legal reason to be there than cant refuse to leave.. Just remember youll never win an arguement on the street, be polite tell them they dont have your consent and that youd like them to leave. Theres alot more to it, but if you want to kow ask them why they have the right to be there, and then do some research on the topic. there is a bunch of case law out there, and most of its availible on the net.