Evaluation of Rhodamine B as a biomarker for assessing bait acceptance in wild pigs

Abstract

Worldwide, there is growing interest in the use of pharmaceutical baits to control populations of wild pigs (Sus scrofa). In this study we evaluated the utility of Rhodamine B (RB), a chemical marker commonly used in wildlife research and management, as a potential biomarker for quantifying bait uptake in wild pigs. Thirty wild pigs were live-trapped, transported to a captive facility on the Department of Energy's Savannah River Site located in South Carolina, USA, during autumn 2013, and administered RB orally at a dosage of 30 mg/kg. Eight vibrissae and guard hairs were collected pre-and post-RB exposure (7 or 14 days) and evaluated for the presence of RB using fluorescence microscopy. No evidence of RB marking was observed in any samples collected pre-RB administration. In contrast, we observed fluorescent marking post-RB exposure that was indicative of the presence of RB for all individuals, with 98% of vibrissae and 100% of guard hairs exhibiting RB marks. The uniform detection of RB among individuals and consistent manifestation of marks in both guard hair and vibrissae, samples that easily can be collected and stored by untrained field personnel from live or deceased pigs, suggests that RB is an effective biomarker for use in large-scale management programs to control wild pigs. In particular, our results, combined with previous studies evaluating uptake of RB in other species, suggest that RB can be used to develop baiting programs to deliver pharmaceuticals to free-ranging wild pigs, as well as evaluate the potential impacts of pig baits on nontarget species. Ó

Exposure of a population of invasive wild pigs to simulated toxic bait containing biomarker: implications for population reduction

“…In particular, adding a biomarker to the placebo bait can provide valuable understanding of the potential for a simulated deployment of SN toxic bait to expose a population of wild pigs to the toxic bait and possible lethal effects. The biomarker, rhodamine B (RB), has been demonstrated to be an effective biomarker for marking the vibrissae of wild pigs 39,40 14 days after consumption, 39 and without being aversive or toxic to wildlife. 41 Our objective was to evaluate population-level exposure of wild pigs in a natural ecological setting to placebo bait using a biomarker in lieu of the toxic ingredient, SN.…”

Effects of Rhodamine B on Palatability of Invasive Wild Pig Baits

“…Thus, additional information regarding the detection and persistence of RB as a biomarker in HOGGONE ® placebo was not gathered. Results from recent studies on the efficacy of RB as a biomarker in invasive wild pigs coupled with results of this study would indicate, though, that RB is an effective biomarker for invasive wild pigs (Beasley et al 2015, Webster et al 2017, Baruzzi et al 2017.…”

“…The addition of RB to food items which were known to be palatable to particular species, such as coyotes (Canis latrans) and brush tailed possums (Trichosurus vulpecula), has been shown to reduce the palatability of those baits and in some cases resulted in rejection of baits entirely Pan 1981, Morgan 1981). Recent studies have shown the efficacy of RB as a biomarker in invasive wild pig baits (Beasley et al 2015, Webster et al 2017, however, only two allowed for the conscious consumption of RB baits and they did not directly address palatability of RB when added to baits known to be palatable to invasive wild pigs (Fleming et al 2000, Baruzzi et al 2017.…”

Effective dose and persistence of Rhodamine‐B in wild pig Vibrissae

“…The captive care facility consisted of covered 2.5 × 3‐m or 2.5 × 6‐m pens constructed of high‐quality chain‐link fencing with a concrete floor (Beasley et al 2015 b ). We placed pigs in individual pens except for juveniles that were trapped together, which we housed in the same pen (2.5 × 6 m).…”