That's odd, since I wasn't using it in a plural sense. Anyway, we can probably move on. More often than not it goes bad, but it's true, sometimes it works well. But this is a different issue. You seem to have flipflopped from wanting to replace brown snakes to wanting to control vermin. You literally said you wanted to replace a lethal snake with a non lethal snake. You are now completely changing what you said you wanted to do. It's fine to say 'okay, maybe that wouldn't work but how about this' but it gets a bit tedious when you pretend you were saying something completely different. Look at your first post. It's quite blunt and obvious. South east QLD is loaded with native snakes including very common non venomous species which love to eat rodents and house geckoes, as well as a snake which can sort of eat cane toads (keelbacks are often said to be able to do it, but it's sort of like I can drink vodka or beer if I want to. It won't kill me if I do it a bit, but apart from recreation, I'm much better off drinking water or milk or tea. Cane toads don't kill keelbacks but they don't do as well on them and much prefer other prey. The same is true of snakes which are sympatric with toads. Any snake which eats toads is going to prefer a far less toxic native frog, so they're going to reduce frog numbers before switching to toads. Crows also eat toads, but again, there are other things they prefer. The important thing about biological control is that it needs to be very target specific, and nothing particularly likes eating toads and anything which does eat them will prefer frogs. This fundamentally rules out all predators as appropriate candidates for biological control of toads (huge funds and brilliant minds have spent decades on this issue and the most prominent one has given up and said we just need to get used to living with them - don't get your hopes up about being able to just say 'oh, how about rat snakes' and save the world. What we seem to be seeing here is a very obvious example of the common concept of some knowledge being more destructive than none. It's cool that you're exploring ideas, but you're getting ahead of yourself and acting like you know more than you do. By all means explore ideas, but you need to be willing to accept realities when you find them rather than knowing a little bit, coming up with an idea, and stubbornly sticking with it even when clearly shown it is completely wrong. By all means study more, learn more, think more, develop ideas, that's great, but stay genuine rather than pretending you meant something other than what you did, keep an open mind, and I'd encourage you to do a lot more study if you want to continue on with this path, as the holes in your knowledge are causing you to say some very incorrect things. As we all (at least should!) know, biological control is an extremely hazardous thing with the potential to do far more harm than good, and you've demonstrated that you haven't learned much if anything about how to select species or identify potential problems in candidate species. You'd do well to study about this topic.