Making best use of rat poison

Forest and Bird, Issue 294, 1 November 1999, Page 12

Making best use of rat poison

—Kathy Ombler.

review of the use of the poison bait brodifacoum on conservation land is being conducted by the Department of Conservation. The poison is virtually the only weapon the department has in its battle against burgeoning populations of rats, and officials want to ensure it is used properly and wisely. In DoC’s island eradication programmes, the pesticide brodifacoum is considered a valued and cost-effective ally. (See An Eradication of Rats, page 36.) According to a senior technical officer of the department, Keith Broome, no other pesticide is as effective in island situations. ‘As well as ridding islands of rats, brodifacoum can also be useful for mopping up bait-shy possum populations where the pest has learned not to eat other poisons, he says. Brodifacoum, marketed as

Talon and Pestoff, is a ‘secondgeneration anti-coagulant which is currently available without licence in New Zealand. (It is sold in supermarkets.) The poison is also used by farmers, forestry companies, community conservation groups and regional councils. ‘Correctly applied, animals poisoned with brodifacoum do not get symptoms until after they have a lethal dose. This means rats don’t become baitshy and it allows us to get the 100 percent kill that is so critical on islands, Keith Broome says. However, he explains, this helpful property of brodifacoum can potentially cause problems because the poison can be transferred to scavengers or predators of the rat or possum. ‘Generally this transfer results in low levels of poison causing no apparent harm, but if used repeatedly small doses

could build up. While DoC is keen to retain the use of brodifacoum for island situations, where ‘oneoff’ poison operations do not constitute the same risk as that of repeated use on the mainland, it wishes to improve its use of brodifacoum generally, with better safety procedures. ‘The department is currently researching alternatives and ways to better manage the "when, how and why" of pest control using brodifacoum, Keith Broome says. ‘A review

team is looking at current use of the pesticide and developing practical solutions while maintaining a high level of protection. ‘The department is also initiating a programme to better inform people about its pest control operations. These procedures build on the best of what is already happening in some areas and set nationwide standards for pesticide use on public conservation land.’