I'm sure rats and mice and other vermin would work as well. Then you could make a little extra catnip money, and have fun at the same time.
Or inner city kids could clean the place up by bringing in rats and collecting the rat bounty. Oh, but that might require letting them use pellet guns or even .22 rifles. Can't have that.
Country kids can bring in tree rats instead. It might also prove the solution to the urban Goose and Deer problems.
Nip head!