Deterring non-target birds from toxic bait sites for wild pigs

Abstract

Toxic baiting of wild pigs (Sus scrofa) is a potential new tool for population control and damage reduction in the US. Field trials testing a prototype toxic bait (HOGGONE 2 containing 5% sodium nitrite [SN]), though, revealed that wild pigs spilled small particles of toxic bait outside of bait stations which subsequently created hazards for non-target species that consumed those particles, primarily passerine birds. To deter non-target birds from consuming particles of spilled bait, we tested four deterrents at mock bait sites (i.e., baited with bird seed) in north-central Colorado, USA during April–May 2020. We found a programable, inflatable deterrent device (scare dancer) reduced bird visitation by an average of 96%. Then, we evaluated the deterrent devices at SN-toxic bait sites in north-central Texas, USA during July 2020, where the devices were activated the morning following deployment of SN-toxic bait. Overall, we found 139 dead wild pigs at 10 bait sites following one night of toxic baiting, which represented an average of 91% reduction in wild pigs visiting bait sites. We found that deterrent devices were 100% effective at deterring birds from toxic bait sites. We found two dead non-target mice at bait sites without deterrent devices. We noted that deploying toxic bait in mid-summer rather than late-winter/early-spring reduced hazards to migrating birds because they were not present in our study area during July. We recommend using deterrent devices (i.e., novel, programmable, battery operated, continuous and erratic movement, and snapping sounds) to reduce hazards to non-target birds at SN-toxic bait sites. We further recommend deploying SN-toxic bait during seasons when migrating birds are not as abundant until further research demonstrates minimal risks to migrating birds.

Assessment of spilled toxic bait by wild pigs and potential risk to non‐target species

“…Wild pigs quickly acclimated to bait box B in all trials, and moving the bait box several meters before deploying toxic baits is now standard practice in field applications during research trials. In addition, Snow et al 27 . reported that a combination of seasonal application (i.e.…”

“…summer deployment rather than winter), the use of scare devices activated ~ 1 h before sunrise the morning after toxic deployment, and cleaning and spreading fresh topsoil across the area immediately adjacent to the bait station the morning after toxic deployment eliminated observed avian mortalities at bait sites in Texas. Although we would recommend cleaning bait sites as describe in Snow et al 27 as a best management practice associated with bait deployments, it will probably not eliminate the risk to all non‐target individuals. The double‐observer surveys described in this study were designed to maximize detection of spilled baits.…”

Estimating body mass of wild pigs (Sus scrofa) using body morphometrics

“…14–100 for Mississippi samples). Measurements collected by USDA personnel were done conducted by following several USDA IACUC‐approved studies (Sanders et al, 2020; Snow et al, 2019; Snow et al, 2022; Snow, Halseth, et al, 2021; Snow & VerCauteren, 2019; Snow, Wishart, et al, 2021). Body mass and other morphometric data were gathered postmortem.…”

Alternatives to corn for baiting wild pigs

“…We attempted to offer test baits and corn ad libitum to avoid biasing a wild pig's choice. The amounts of baits offered were based on corn consumption rates from previous wild pig trials in our facility (Snow et al 2021). In every offering, earthworms were consumed prior to trial end thereby biasing earthworm results negatively.…”

“…Corn may become less attractive as alternative food resources in an area become more abundant (Barrett and Birmingham 1994). Additionally, corn attracts a variety of other species (Snow et al 2021), resulting in decreased efficacy for wild pigs or endangerment of nontarget species. Finding alternative baits to corn may help wildlife managers increase and target wild pig visitation to bait sites, especially during seasons when corn is less effective.…”