Rabid/violent feral cats killed my duck in Southern MEXICO last night my dog must be next.?

They tore ducks house apart. I've tried to "humanely" control them and I don't feed them. I have a 12 feet HIGH concrete enclosure complete with glass shards embedded in the concrete but the violent cats jump onto the roof from someone else's roof and into my backyard. There are NO humane traps or Vets who sell traps here in MEXICO this a very small town in Southern MEXICO. The closest big city is 500 miles away. My dog does not like inside the house because it's hot because I don't have air conditioning here in Southern MEXICO. Will someone PLEASE read this question and answer how to rid myself of over 2 dozen feral cats or should I allow them to kill my domesticated dog? PLEASE no more "silly thinking I live in Brooklyn with an animal control agency" animal rights activists. This is a real issue. Can someone suggest an odorless poison to mix with the tuna I have?