Most rat baits are toxic to other animals if they happen to chew or chomp on a dead rat. This is a deadly but non-toxic method to kill rats by using Instant Potato flakes or powder. Here in Australia they are marketed as "Deb" Instant Potato and there are also generic or 'home' brands available. The brand doesn't matter at all.
Simply make a small opening in the sachet so the rats get a smell of it and place it in a dry place where the rats can find it. The rats will gorge themselves on it and it makes them thirsty. When they take a drink, the potato flakes/powder expands to many times in size and it bursts the gut of the rat and they die instantly. It's no more painful than the slow death by internal bleeding that is caused when the usual rat baits are used and if an animal happens to pick it up there's nothing toxic that can harm them.
Source: My local Nurseryman who uses this method to safely kill the rats that eat his young vegetable plants.
By Lois 
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The idea is to place the packets discreetly in areas where only rats or mice would likely be crawling. Other animals don't usually pick up the toxic baits either if the bait is placed carefully. Once the rat or mouse is dead there's no chance of the powder or flakes expanding any further.
By Barb. Lehto04/16/2013
The instant potatoes expand when coming into contact with the liquid the rat/mouse drinks after eating them. Once expanded, they don't continue to expand, so don't endanger anything else that would eat the dead animal. This seems good, safe & probably even less expensive than the usual rodent poisons.
Yeah, I'm not so sure this would be safe for other animals to ingest either.
Primarily because rats and mice have a one way digestive system, and they can't burp or vomit. The same effects happen when you feed them soda, the carbonation causing them to swell up. Both are good ways to keep the population down and not endanger other critters.
I'm curious as to why if the potato flakes/powder expands to many times in size in a rat it would not act the same way in other animals and birds. Does anyone know?
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