Re‐Use or Refuse? The Stability of Para‐Aminopropiophenone (PAPP) and Sodium Fluoroacetate (1080) in Canid Pest Ejector Capsules

Abstract

Toxins for vertebrate pest control in bait material degrade under field conditions but there are limited data available on the degradation of toxins used in canid pest ejectors (hereafter ejectors). Re-use of non-activated capsules would be practical for end-users and support the optimal and cost-efficient use of vertebrate toxins. This study assessed the degradation of capsules intended for wild dog applications containing sodium fluoroacetate (1080) or para-aminopropiophenone (PAPP) under storage and field conditions in north-eastern Australia (Queensland) and Western Australia. Only 2.6% of 1080 capsules showed any signs of potential leakage, and only a minimal loss of 1080 content occurred over the 2-year study period in Queensland. The rate of degradation was not significantly different between 1080 capsules deployed in the field and those kept in storage, while field-deployed capsules in Western Australia decayed at a faster rate than those kept in storage. Regardless, degradation rates were minimal across both sites, with modelling suggesting that the 1080 content in capsules would still exceed that required for a lethal dose for wild dogs (LD50 = 1.76 mg) for extended periods (~4–9 years). Intact, undamaged PAPP capsules were highly resistant to degradation, with neither stored nor field-deployed PAPP capsule treatments at either site showing any significant loss in PAPP content after 2 years. However, ~4% of PAPP capsules in the Western Australian study suffered physical failure, and subsequently contained only trace amounts of toxin, but could be easily identified for disposal. Collectively and conservatively, our findings support the use of undamaged (and non-activated) PAPP or 1080 capsules for at least 2 years, following careful inspection and subsequent rejection of damaged capsules. These results are reassuring and provide valuable recommendations to inform users on the effective, safe and efficient use (and re-use) of toxic capsules in ejectors for wild canid control.