Bait Preference of Free-Ranging Feral Swine for Delivery of a Novel Toxicant

Abstract

Invasive feral swine (Sus scrofa) cause extensive damage to agricultural and wildlife resources throughout the United States. Development of sodium nitrite as a new, orally delivered toxicant is underway to provide an additional tool to curtail growth and expansion of feral swine populations. A micro-encapsulation coating around sodium nitrite is used to minimize detection by feral swine and maximize stability for the reactive molecule. To maximize uptake of this toxicant by feral swine, development a bait matrix is needed to 1) protect the micro-encapsulation coating so that sodium nitrite remains undetectable to feral swine, 2) achieve a high degree of acceptance by feral swine, and 3) be minimally appealing to non-target species. With these purposes, a field evaluation at 88 sites in south-central Texas was conducted using remote cameras to evaluate preferences by feral swine for several oil-based bait matrices including uncolored peanut paste, black-colored peanut paste, and peanut-based slurry mixed onto whole-kernel corn. These placebo baits were compared to a reference food, whole-kernel corn, known to be readily taken by feral swine (i.e., control). The amount of bait consumed by feral swine was also estimated using remote cameras and grid boards at 5 additional sites. On initial exposure, feral swine showed reduced visitations to the uncolored peanut paste and peanut slurry treatments. This reduced visitation subsided by the end of the treatment period, suggesting that feral swine needed time to accept these bait types. The black-colored peanut paste was visited equally to the control throughout the study, and enough of this matrix was consumed to deliver lethal doses of micro-encapsulated sodium nitrite to most feral swine during 1–2 feeding events. None of the treatment matrices reduced visitations by nontarget species, but feral swine dominated visitations for all matrices. It was concluded that black-colored peanut paste achieved satisfactory preference and consumption by feral swine, and no discernable preference by non-target species, compared to the other treatments.

Attractants for wild pigs: current use, availability, needs, and future potential

“…This reward, ample supply, and/or timely resupply of the attractant increase the probability of repeat visitation by wild pigs to an attractant site. Previous research demonstrated a black-colored peanut paste performed equally as well as whole-kernel corn for eliciting wild pig visitations though it was noticeably more fragrant (Snow et al 2016b). Further, Campbell et al (2006) concluded that peanut-based attractants elicited more visitations by wild pigs than raccoons (Procyon lotor) or collared peccaries (Pecari tajacu).…”

“…Food attractants targeting smell and taste Recently, there has been a focus on identifying preferred attractants for wild pigs designed for the delivery of pharmaceuticals or toxicants Campbell and Long 2007;Snow et al 2016b). Most attractants attempt to exploit the sense of smell, because it is renowned as the most developed sense of wild pigs.…”

“…Legumes including chufas (Cyperus esculentus) and peanuts are highly desired regionally and sought by wild pigs (W. Gaston and M. Ondovchik, USDA APHIS WS, personal communication). Further, peanut paste and peanut waste are often effective as attractants for wild pigs when available (West et al 2009;NFSDMP 2016;Snow et al 2016b). After mechanical separation, peanut waste, consisting of hulls, skins, leaves, stems, and residual amounts of nuts, is highly odiferous and can serve as an excellent attractant (B. Ferris, USDA APHIS WS, personal communication).…”

“…While wild pigs are not generally territorial and do not actively defend an exclusive area, they do have mating and dominance behaviors similar to wild ungulates, which could make them susceptible to decoy use in hunting scenarios (Mayer and Brisbin 2009 Several extensive research efforts focusing on attractants for wild pigs have been conducted over the last few decades (Supplemental Tables 2 and 3) (Wathen et al 1988;Campbell and Long 2008;Snow et al 2016b); however, conclusive results defining the most effective attractants are lacking (Wathen et al 1988;Mitchell 1998;Hartin et al 2007;Campbell and Long 2008). Researchers in Spain have been working toward developing baits (consisting of grainy piglet feed, sodium chloride, sacarose, and cinnamon-truffle powder) and a deployment strategy for vaccinating susceptible young wild piglets against bovine tuberculosis (Ballesteros et al 2011).…”

“…Use of attractants for oral delivery of toxicants or bioactives such as vaccines and oral contraceptives to free-ranging wildlife for population control is receiving increasing attention; however, efficacy and feasibility of delivery systems should be determined before operational activities are implemented Campbell et al 2013;Ferretti et al 2014;Snow et al 2016b). Challenges associated with these efforts are compounded when delivery to non-target species is unacceptable or problematic, hence the need for wild pigspecific delivery devices.…”