Field evaluation of low-dose warfarin baits to control wild pigs (Sus scrofa) in North Texas.

Richard M Poché,Larisa Polyakova,Greg Franckowiak,Daniel J Somers,Lindsay N Briley,Batchimeg Tseveenjav,David Poché,Govindhaswamy Umapathy

doi:10.1371/journal.pone.0206070

Abstract

Wild pigs (Sus scrofa) are a highly detrimental invasive species that occupy a rapidly expanding range within the United States. In Australia, field trials evaluating baits containing 0.09% warfarin resulted in wild pig population reduction >95%. The objective of this study was to conduct an EPA-approved field trial to evaluate the use of bait containing low-dose warfarin (0.01% and 0.005%) in reducing wild pig numbers in Texas. An 8-week field test was conducted in the panhandle ~100 km southeast of Amarillo. Two ~8 km2 treatment plots were selected and each presented with either 0.01% or 0.005% warfarin baits. One control plot (~8 km2) was presented placebo. The baits were delivered using 30 species-specific feeders per plot (n = 90) that kept wildlife from accessing the toxicant. Pig movements and feed consumption were monitored during pre-treatment, treatment, and post-treatment periods. All pigs with VHF transmitters within the 0.005% warfarin-treated plot (n = 14) succumbed to the warfarin (100% mortality). Overall, 35 wild pigs were found dead from warfarin toxicosis, within both treatment plots. Total feed consumption by wild pigs was reduced by ~97.8% and ~96.2% for the 0.005% and 0.01% warfarin baited plots, respectively, indicating the absence of pigs was a result of toxic bait consumption. Results of 97 systematic searches of the treatment plots indicated no warfarin-induced non-target wildlife fatalities. Warfarin residues in wild pig livers averaged 3.69 mg/kg (n = 13) and 2.89 mg/kg (n = 9) for pigs recovered within the 0.005% plot and 0.01% warfarin plot, respectively. This study is the first efficacy field evaluation of a wild pig toxicant conducted in the US. The results suggest low-dose warfarin bait, presented in species-specific feeders, can effectively reduce wild pig numbers and pose minimal risk to non-target wildlife and domestic animals. A product containing warfarin may provide another management tool in reducing wild pig problems.

Highlights

The wild pig (Sus scrofa,) is an invasive species, with one of the widest global distributions of any animal [1], extending to all continents except Antarctica [2,3]
Sixty-one (61) captured wild pigs were fitted with radio-tracking devices during the 39-day trapping period before study initiation, with very high frequency (VHF) and global positioning system (GPS) transmitters applied to 50 and 11 pigs, respectively (Table 2)
When initiating a vertebrate pest control program two important questions should be asked: 1) is the specific vertebrate control necessary, and 2) do the benefits outweigh the potential for harm [73]? First, given the global burden invasive wild pigs present, it’s difficult to argue against the need to control them, and the results of the current study suggest that 0.005% warfarin bait can reduce wild pig abundance markedly (>90%) in areas where it is applied

Summary

Introduction

The wild pig (Sus scrofa,) is an invasive species, with one of the widest global distributions of any animal [1], extending to all continents except Antarctica [2,3]. The specific roles of these authors are articulated in the ‘author contributions’ section

Objectives

Methods

Results

Discussion

Conclusion