“If you need to drive over it to spread mouse bait, you lose $35 of grain per hectare with wheels running over it,”
They think that mice were reintroduced accidentally by campers, when mice stowed away in camping gear. I was standing there thinking that they could very easily spend millions to eradicate the population only to have it reintroduced intentionally or in another accident six months later.
The biggest issue with poisoning operations is when the animals become bait shy, then it dramatically reduces kills, hence the popularity of warfarin for rodents - they don't associate the poisoning with ingesting the bait, so don't become bait shy.
I suspect in smarter social animals, bait shyness could be passed along as communal knowledge. In NZ we also use "pre-feeding" where the baits, without poison, are dropped for some time to teach the target species that they're good eating.
Predator by-kill can be a real issue though, and I guess it depends on whether the predators are pests also - like foxes and cats in Australia, mustelids in NZ. There's a reason NZ is the biggest user of 1080, there's no carnivorous mammals in our forests that we want to stay there, so if they eat a poisoned possum or rodent, bonus.
That said, Australia has carnivorous marsupials that are highly endangered, so it'll be a different ballgame over there.