Lily Brown, of East Taireri, asks :-

What happens to poison once rabbits eat it? Do hawks and other predators get poisoned?

Penny Fisher, an ecologist with Landcare Research, responded.

Two poisons are currently used in New Zealand for rabbit control, sodium fluoroacetate (also known as 1080) and pindone (an anticoagulant). Because each acts as a poison in quite different ways, they also have different fates in animals’ bodies after they are eaten.

With 1080 poisoning, rabbits usually die in less than 12 hours, so there is often toxic bait still present in their gut contents. There will also be varying concentrations of 1080 present in the rest of the body, with highest concentrations in muscle (particularly the heart), of rabbits that have died of 1080 poisoning.

With pindone poisoning rabbits can take a few days to die after eating a lethal amount of bait, so there is usually not any toxic bait present in their gut when they die. Residues of pindone will be most concentrated in the liver, but also present at lower concentrations in muscle and fat of rabbits that have died of pindone poisoning.

Scavenging birds like hawks and falcons, and mammals such as dogs, cats, ferrets and stoats may be secondarily poisoned if they feed on the carcasses of poisoned rabbits. The risk of this depends on how much they find and eat, and how freshly dead the rabbit is. The risk to scavengers declines over time as rabbit carcasses rot and become less toxic as the residues in them degrade. We know a lot more about 1080 in this regard, for example there is a well-known high risk to dogs from scavenging 1080 poisoned carcasses, but there is less information about the secondary risks of pindone