Acceptance by stoats (Mustela erminea) of 1080 (sodium monofluoroacetate) in small-volume baits and its effect on behaviour and time to death

Abstract

AIMS: To assess whether stoats (Mustela erminea) would eat small baits containing 0.1% sodium monofluoroacetate (1080); whether they would die from it; how long it would take to kill them; and to document the behaviour of 1080-intoxicated stoats.

METHODS: Stoats were offered 1-g baits of two semi-fluid formulations containing 0.1% 1080, presented in open dishes, and their subsequent behaviour was monitored by video and direct observation. Muscle samples from stoats that died were analysed for 1080 residues.

RESULTS: There was no significant difference between two types of bait with regard to acceptance, mortality, and time to death, and behavioural effects were similar; consequently, results from the two types of bait were combined. Twelve of 14 stoats offered the baits ate them voluntarily, and a 13th licked bait off its fur; all 13 died between 1 h 15 min and 4 h 7 min (mean 2 h 38 min) later. At first (range 29 min — 2 h 7 min, mean 1 h 1 min), their behaviour appeared to be normal. Ataxia and hyperactivity were the first behavioural signs of poisoning, and lasted 2 min — 1 h 40 min (mean 26 min). This was followed by recumbency with convulsions and rapid breathing (range 16 min to 2 h, mean 58 min), then recumbency with limited activity and progressively shallow breathing prior to death (range 1–51 min, mean 33 min). Stoats became non-responsive to a light being turned on, or to touch once recumbency became sustained.

Residues of 1080 were found in muscle tissue of all 13 dead stoats, at concentrations ranging from 0.075 μg/g in a 287-g male that died 4 h 7 min after eating only 0.74 g of bait, to 2.5 μg/g in a 254-g female that died 2 h 42 min after taking a whole 1-g bait.

CONCLUSION: Stoats will voluntarily take small (1-g) baits containing a lethal dose of 1080 at 0.1%, and die from it comparatively rapidly for a mammalian carnivore.

KEY WORDS:

• Stoat
• Mustela erminea
• pest control
• animal welfare
• sodium monofluoroacetate
• 1080
• intoxication
• behaviour

Acknowledgements

We thank Rod McDonald, HortResearch Bioengineering, for making up the baits; Bill Simmons, Animal Control Products, for supplying the 1080 and adding it to the baits; Paul Chambers, Massey University, for anaesthetising the stoats for pre-trial inspection; Kevanne McGlade, for invaluable assistance throughout the study; Kate McArthur, for help with processing videotapes; and Tracy Harris and Kiryn Weaver, for assistance with feeding and monitoring the stoats. The manuscript benefitted greatly from the input of three anonymous referees. We thank The Department of Conservation for financial support.

Notes

¹ The Scentinel® research was conducted by scientists in the BioEngineering group of HortResearch based at Ruakura Research Centre. The two principal researchers involved were Mr Rod McDonald, of HortResearch, and Dr Carolyn King, who at the time of the research had a 50:50 HortResearch:University of Waikato appointment. By agreement with HortResearch, the Scentinel will be further developed, manufactured and made available to conservation groups, farmers and other potential users, by Technology Transfer Ltd (TTL), an entity established for this purpose. For further information on TTL, contact Mr Tony Brenton-Rule, at 0064-4-5627895, mobile [phone], or by email at [email protected]

² E Gould, HortResearch Bioengineering Technologies, Hamilton, New Zealand

³ KE Littin, Ministry of Agriculture and Fisheries, Wellington, New Zealand