Evaluation of Feral Swine-Specific Feeder Systems

Abstract

Feral swine (Sus scrofa) have been introduced across many portions of the globe, including rangeland ecosystems of the United States. Feral swine populations are expanding because of their adaptability, high reproductive potential, and because they are (accidentally and intentionally) released by humans. Today, feral swine are the most abundant exotic ungulate in the United States.1 Rangeland ecosystems are impacted by feral swine primarily through soil disturbance caused by rooting activities. Within these systems, natural disturbances (e.g., burrowing, grazing by native animals, and periodic fi re) generally increase or maintain species diversity.2 However, rooting by feral swine often occurs at intensities and frequencies that do not mimic natural disturbances and can have negative impacts, such as disseminating exotic plant species and reducing native plant species diversity.3 Feral swine damage to livestock enterprises within rangeland ecosystems is direct (e.g., predation) and indirect (e.g., destruction of fencing and disease transmission) and both cause substantial economic losses.4 In Australia, predation on lambs often is widespread and is infl uenced by feral swine density.5,6 Feral swine predation on livestock is also a problem in the United States in localized regions.7 Furthermore, Seward et al. (2004) recommend close monitoring of livestock and confi ning preparturition animals prior to calving and lambing to minimize risks of predation by feral swine.4 Tools available to control feral swine damage have not been universally successful.8 New methods, such as fertility control agents, vaccines, or toxicants, are needed and will require an oral delivery system for effective administration to feral swine populations.1 Prior investigations of baits intended for pharmaceutical delivery to feral swine in the United States have found that the concept is feasible,9 but that there are challenges in developing species-specifi c baits for feral swine.10,11 These studies have led to the creation of relatively inexpensive prototypes of nontarget exclusion feeder systems (NEFS) for feral swine. None of these feeder systems has been evaluated in the United States. Our overall objective was to evaluate candidate NEFS for feral swine as a means to deliver baits containing pharmaceuticals. Our specifi c objective was to compare feral swine and nontarget animal consumption events at three different feeder systems in a rangeland ecosystem of southern Texas. Given the successes of the Boar-Operated-System (BOSTM) feeder in the United Kingdom,12 we hypothesized that this unit would be specifi c to feral swine in southern Texas.