Populations of invasive wild pigs (Sus scrofa) are increasing in many regions of the world, in particular the United States and Australia. Invasive wild pigs cause extensive damage to ecological resources and agriculture. Development and registration of a safe and humane toxic bait offers a practical and cost‐effective tool to control invasive species. Currently, no toxicants are approved for use on invasive wild pigs in the United States and those approved in Australia are under scrutiny because of concerns regarding humaneness and effects on nontarget species. We tested a newly formulated bait containing the micro‐encapsulated active ingredient, sodium nitrite (HOGGONE®; Animal Control Technologies Australia P/L, Victoria, Australia), that is considered humane and safer for nontarget species because it does not bioaccumulate. We examined palatability, lethality, and stability of the bait (i.e., fresh compared to 8‐month‐old bait) on groups of captive invasive wild pigs. We found HOGGONE® was a preferred food item, averaging 475 g of toxic bait consumed per animal during the first night offered. Consumption of HOGGONE® resulted in 95% mortality (53 of 56) in the treatment groups across 2 treatment nights. Most mortalities (98%) occurred during the first night the toxic bait was offered. Camera evidence suggested that deaths occurred within 3 hr post‐offering. The toxic bait was stable and effective up to 8 months post manufacture. Our results support current applications to register HOGGONE® for reducing damage from invasive wild pigs in the United States and Australia. Further research is required to evaluate HOGGONE® on free‐ranging invasive wild pigs using bait stations that exclude nontarget species. © 2017 The Wildlife Society.

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.

BACKGROUND Wild pigs (Sus scrofa) are a destructive invasive species throughout many regions of the world. In 2018, a field evaluation of an early prototype of a sodium nitrite (SN) toxic bait in the United States revealed wild pigs dropped large amounts of the toxic bait outside the pig‐specific bait stations while feeding, and thus subsequent hazards for non‐target animals. We modified the SN‐toxic bait formulation, the design of the bait station, and the baiting strategy to reduce dropped bait. We tested the modifications in Queensland, Australia (December 2018), Alabama, USA (August 2019), and Texas, USA (March 2020) under differing climatic and seasonal conditions for one night. RESULTS Cumulatively we found 161 carcasses of all age classes of wild pigs using systematic transects. Remote camera indices indicated high lethality for wild pigs, achieving population reductions of 76.3 to 90.4%. Wild pigs dropped only small particles of SN‐toxic bait (average = 55.5 g per bait site), which represented a 19‐fold decrease from the previous trial. Despite this reduction, we found three Australian ravens (Corvus coronoides) in Queensland, two Virginia opossums (Didelphis virginiana) in Alabama, and 35 granivorous‐passerine birds (mostly dark‐eyed juncos [Junco hyemalis]) in Texas dead from consuming the dropped bait. We did not detect any population‐level effects for those species. CONCLUSION Our modifications were effective at reducing populations of wild pigs, but the deaths of non‐target species require further steps to minimize these hazards. Next steps will include evaluating various deterrent devices for birds the morning after SN‐toxic bait has been offered. Published 2020. This article is a U.S. Government work and is in the public domain in the USA

Summary. Lymphatic vessels draining the uterus and ovaries were located within the mesometrium and along the utero-ovarian pedicle by injection of marker dyes into the uterine wall and/or ovary of sheep and goats. Afferent lymphatics drained from the uterus towards the utero-ovarian pedicle and alongside the uterine artery, while 4\p=n-\12ovarian lymphatics emerged from the sub-ovarian plexus. A complex lymphatic network was formed in the region of the utero-ovarian pedicle by anastomosis between uterine and ovarian lymphatics. Mixed lymph carried in ducts alongside the uterine artery and in the utero-ovarian pedicle drained into the medial iliac node(s) and lumbo-aortic nodes, respectively. There was no evidence for retrograde lymph flow between the uterus and ovaries, but the close proximity of utero-ovarian lymphatics and the ovarian artery may provide an additional pathway for countercurrent diffusion of prostaglandin F-2\g=a\.Afferent lymph collected after chronic cannulation of utero-ovarian ducts ipsilateral to an ovary bearing a corpus luteum contained a mean progesterone concentration which was 10-to 1000-fold higher than that in jugular vein plasma between 15 and 45 days of gestation. Uterine lymph collected after cannulation of utero-ovarian ducts followed by ipsilateral ovariectomy had a progesterone value equivalent to that in plasma. Protein concentration in utero-ovarian and uterine lymph was between 85 and 90% of that of plasma, while Na concentration was slightly higher, and Cl concentration slightly lower than that of plasma. The concentration of K was similar in both biological fluids, confirming that tissue damage of cannulated vessels was negligible. Cell numbers in utero-ovarian and ovarian lymph were low (200 leucocytes/mm3) and consisted mostly of lymphocytes (>94%). These studies show that leucocytes in lymph are exposed to a high concentration of progesterone, and possibly other related steroids, in the utero\x=req-\ ovarian network which is adjacent to an ovary containing a corpus luteum.

Conservative population declines of 73% were recorded in three independent feral pig populations in Welford National Park, Queensland, when PIGOUT ® baits containing 72 mg of sodium fluoroacetate were used in a baiting program following prefeeding. Declines were measured using a prebaiting population census with remote cameras, followed by carcass recovery. The knockdown of susceptible feral pigs may have been higher than this, since any carcasses not recovered reduced the recorded efficacy. In addition, feral pigs know to have left the baiting area after trapping and telemetry-tagging, and subsequently not exposed to toxic baits, were included in the analysis. The use of remote cameras and carcass recovery appears to be a relatively accurate means of recording localised declines in feral pig populations. This method is applicable only when carcass recovery is possible, such as in open areas in the semi-arid rangelands. A decline of 86% of radio-tagged feral pigs attending bait stations was also recorded. Camera observations revealed no non-target consumption of baits. Measurement of sodium fluoroacetate-contaminated tissues from feral pigs showed that residues were too low to present a significant risk to recorded scavenging animals in the area. Some feral pigs vomited before death, with vomitus containing sodium fluoroacetate poison at high concentrations. No vomitus was consumed by non-target species. Almost all feral pigs were killed relatively rapidly after ingestion of sodium fluoroacetate and the signs observed in a small number of poisoned feral pigs did not indicate a significant welfare concern.