Rodent FAQs

These are some of the most common questions (FAQs) asked about rats and mice and how to get rid of them; and the answers.

• Are rodenticide baits better at controlling rats and mice than traps?
  • Yes.
  • Rodents are more likely to interact with baits than with traps.
  • Rodents may become ‘trap-shy’ if they set off a trap without being caught; those individuals will then be very hard to catch.
  • Rodenticides are slow-acting to prevent ‘bait-shyness’; by the time an anti-coagulant starts to take effect the rodent will have had many lethal doses.
• Will the dead rodent cause a bad smell?
  • Dead rodents only release an unpleasant smell when they die somewhere warm and poorly ventilated. Most will die unseen and desiccate quickly without odour or cause for concern.
  • Where there is a concern over the risk of unpleasant smells we recommend the use of snap traps at the same time as rodenticide baits; when rodenticides begin to take effect, the rodents become more likely to be caught in traps and can be removed.
  • Not dealing with a rodent infestation increases the risk of bad smells as rodent numbers increase and rodents die from natural causes.
• What is the risk to pets that catch rats or mice that have been poisoned by rodenticide baits?
  • Domestic cats and dogs may catch occasional rodents as part of their natural hunting behaviour. Most will not catch the rodents to consume them.
  • Dogs and cats would have to consume several rodents per day that had recently been poisoned or consumed rodenticide to be at any significant risk of secondary poisoning. Rodenticide poisoning is much more likely to be from accidental direct ingestion of baits that have not been placed in safe locations such as bait stations.
  • First-generation anticoagulant rodenticides (FGARs) such as coumatetralyl (NO Rats & Mice Bait Blocks and Dual Action Bait & Powder) are more rapidly broken down in the livers of rodents and so these are safer (pose a lower risk of secondary poisoning).
• The rat I see every day running along the fence has been eating all the bait I put out, but it is still there after 2 weeks, what is wrong with the bait?
  • Nothing is ‘wrong’ with the bait.
  • Rats and mice are normally nocturnal (active at night). Only in situations where there are many rodents competing for food and other resources are they forced to be active during the day. So, seeing rats or mice during the day is strongly indicative of a large population.
  • Rodents are neophobic (fearful of new things in their environment) and may take a few days to begin feeding on bait.
  • Rodents have a feeding hierarchy, so dominant individuals may prevent subordinates feeding on baits. Only when the dominant individuals are dead can the subordinates begin feeding.
  • Anti-coagulant toxins take 2-5 days to kill the rodents.
  • So, it can take two weeks or longer to get rid of a population.
•  Why should I use baits? I’ll just buy a plug-in repeller.
  • Electric (Electromagnetic [EM]) and sonic rodent repellers will not chase rodents out of a house that they have set up home in.
  • Rodents may reduce activity for a period (usually 2 weeks) when a repeller is used, after this, they become used to the sound/EM effects and return to normal behaviour.
  • Repellers may have some preventative effect, but the pressure to find food and shelter will often overcome the repellent effect of sound/EM.

David Brittain
Kiwicare