Seasonal Efficacy and Risks from a Sodium Nitrite Toxic Bait for Wild Pigs

Authors

Nathan P. Snow, USDA APHIS WS NWRC Fort CollinsFollow
Michael P. Glow, USDA APHIS WS NWRC Fort Collins
Justin A. Foster, Texas Parks and Wildlife Department
Kurt C. VanCauteren, USDA APHIS WS NWRC Forth CollinsFollow

ORCID IDs

VerCauteren 0000-0002-4783-493X

Date of this Version

2024

Citation

Pest Management Science (2024): 1-11

doi: 10.1002/ps.8025

Comments

United States government work

Abstract

Background
Wild pigs (Sus scrofa) are an invasive and destructive species throughout many regions of the world. A sodium nitrite (SN) toxic bait is currently used in Australia and being developed for use in the US and other countries to combat the increasing populations of wild pigs. In the US, efforts to modify the Australian SN-toxic bait and baiting strategy have focused on reducing issues with non-target animals accessing the SN-toxic bait spilled outside of bait stations by wild pigs. We tested and compared modifications for efficacy (with wild pigs) and hazards (with non-targets) in north-central Texas, US during summer (July 2021) and winter (March 2023) seasons.

Results
During both seasons we found that visitation to the bait sites declined 94–99% after deploying the SN-toxic bait, and we found a total of 106 dead wild pigs, indicating considerable lethality for the local population. Prior to deploying the SN-toxic bait, Global Positioning System (GPS)-collared wild pigs were more likely to cease visiting bait sites during summer when foraging resources were abundant. Farrowing decreased visitation to bait sites during the winter. We observed no dead non-targets during summer; winter results showed an average of 5.2 dead migrating birds per bait site (primarily Darkeye juncos [Junco hyemalis]) from consuming SN-toxic bait spilled by wild pigs. The presence and winter-foraging behaviors of migrating birds appeared to increase hazards for those species.

Conclusion
The current formulation of SN-toxic bait was effective at removing wild pigs during both seasons, however it is clear that different baiting strategies may be required in winter when migrating birds are present. Baiting wild pigs prior to farrowing during the winter, and during drier summers, may further improve efficacy of the bait. Reducing hazards to non-targets could be achieved by refining the SN-toxic bait or modifying bait stations to decrease the potential for spillage, decreasing environmental persistence if spilled, or decreasing attractiveness to migrating birds.