You must have been horrified at the idea of using ducks as dog toys, CR. I've found that different species coexist beautifully once they're used to each other. After an initial period of confusion, my cats were always very nice to the chickens and guinea pigs in my garden. I don't have chickens or guinea pigs out there anymore, but the cats never bothered them as much as the neighbors did. One horrible former neighbor strangled my rooster for crowing in the morning.