Review of non‐target hazards associated with rodenticide use in the USA¹

Abstract

Relatively few field studies have been conducted to evaluate hazards to wildlife from rodenticide use. In the USA, field studies have been conducted on both acute and chronic compounds, including zinc phosphide, strychnine, 1080 (sodium monofluoroacetate), and the anticoagulants diphacinone and brodifacoum. Techniques employed in these studies have included carcass counts, direct counts, indirect counts, nest site monitoring, radiotelemetry, habitat and diet evaluation, necropsy, and residue analysis. Although zinc phosphide generally is not secondarily hazardous, it can pose primary hazards, especially to seed‐eating and gallinaceous birds and waterfowl. Strychnine can pose primary hazards, such as to seed‐eating birds; secondary poisoning may be minimal unless predators consume stomach or cheek‐pouch contents of poisoned prey. 1080 can result in primary poisoning, but it especially can pose a secondary hazard to mammalian predators; the risk to raptors is minimal. Anticoagulants are toxic both primarily and secondarily; they can pose a substantial hazard to raptors. Gallinaceous birds, however, are quite resistant to them. Hazards associated with any one rodenticide may vary significantly depending upon use pattern (e.g. commensal vs field). Environmental concerns over rodenticide hazards to wildlife are increasing greatly and will affect future registrations.

Brodifacoum residues in target and non‐target animals following large‐scale poison operations in New Zealand podocarp‐hardwood forests

“…It is extremely persistent in liver and to a lesser extent, muscle tissue (Eason et al 1996). The relationship between the dose of brodifacoum ingested and the level retained in the liver is complex, varies among individuals and is poorly understood (Hegdal & Colvin 1988;Colvin et al 1991). This means that residue levels in liver are difficult to interpret, as residue loads may not be closely correlated with mortality (Hegdal & Colvin 1988).…”

Review of the toxicity and impacts of brodifacoum on non‐target wildlife in New Zealand

“…The perceived hazards of secondary poisoning to non-target wildlife have prevented second-generation anticoagulants such as brodifacoum from being registered for field use in the United States (Colvin et al 1991). However, unlike New Zealand, the United States has numerous species of indigenous small mammals.…”

A review of secondary‐poisoning studies with rodenticides

“…Hence the presented collection is probably not complete. Some of the active substances were reviewed previously (Colvin et al, 1988). Studies where, for specific reasons, poisoned rats were in turn fed to rats have been disregarded here.…”