Delighted to observe that the rat poison we put down was disappearing.
Less delighted to find some weeks later that they had moved it all to a larder in the compost. The poison is Slaymore (as far as I understand it is a standard household rat poison). It comes in the form of blue pellets.
Does this render the compost dangerous to use on a kitchen garden (ie. with all kinds of vegetables)?
Slaymore contains bromadiolone, an anticoagulant that is toxic to rodents and other mammals, as well as poultry and fish.
A data sheet on bromadiolone claims that it will not be taken up by plants in case of spillage. It also talks briefly about cleaning up spills.
Even with this information, I'd be hesitant to apply that compost to anything I'm going to feed my family.
For future use, you may want to investigate bait stations that prevent the rat from removing the bait.
As always, you should always read the label on the rat poison. For my money, if you think poison is around, the things it touches are not food-safe.
As mentioned in another answer, Bromadiolone is an anticoagulant. It is classified as extremely poisonous. When we bought it the packaging said that it would not go up the food chain. This was a lie.
We used it on possums and rats on our previous property that was 10 acres. It came in different pellet sizes for mice, rats, rabbits etc. But birds such as hawks and chicken that fed on these dead animals also died a horrible death. I would not recommend that it be used under any circumstances.
I am sure that the chemical eventually becomes inactive, but it definitely goes up the food chain.
I found this Mouse plague: bromadiolone will obliterate mice, but it’ll poison eagles, snakes and owls, too. I am glad that it supports our findings.
But there is also this that suggests that it has a half life of 14 days in the soil. So it is probably alright in compost. But I would still not use it.