Providing evidence to improve practice

Individual study: Diagnosing the cause of failure to eradicate introduced rodents on islands: brodifacoum versus diphacinone and method of bait delivery

Published source details

Parkes J., Fisher P. & Forrester G. (2011) Diagnosing the cause of failure to eradicate introduced rodents on islands: brodifacoum versus diphacinone and method of bait delivery. Conservation Evidence, 8, 100-106

Summary

Two types of anticoagulant rodenticides have proven successful at eradicating invasive rats and mice from islands. Brodifacoum is the most commonly used and has a low failure rate both when delivered from the air and from ground-based systems. It does, however, present a risk to non-target animals such as birds. When such risk is not acceptable or cannot be mitigated, diphacinone has been favoured by some managers because it is less toxic to birds and less persistent in rodents. However, unlike brodifacoum, diphacinone requires a rodent to eat several baits over several days to ingest a lethal dose. This increases the risk that not all rodents will be killed. When data on attempts to eradicate rats and mice for both aerial and ground-based methods are combined, brodifacoum has a significantly lower failure rate at 17% (54 of 322 attempts) than diphacinone at 33% (13 of 39 attempts). The difference is more significant when just rats are considered. Ground-based methods show similar failure rates for both rodenticides, but to date the very few attempts using aerially sown diphacinone baits have had a high failure rate compared with that for brodifacoum.