David B. Long

Using Baits to Deliver Pharmaceuticals to Feral Swine in Southern Texas

Abstract Few studies have evaluated oral delivery systems of pharmaceuticals (e.g., vaccines, fertility control agents, and toxicants) to feral swine (Sus scrofa) in the United States. Our objective was to assess, through a field trial, the percentage of feral swine and nontarget animals that remove and consume baits intended to transport pharmaceuticals to feral swine in southern Texas, USA. We hand-placed 1,178 iophenoxic acid (IA)–marked baits distributed over 1,721 ha (68 baits/km2) in April 2005 and monitored species-specific bait removal and consumption using track stations, automated camera systems, and serum IA values from captured animals. Ninety percent of baits were removed after 72 hours. For baits for which we determined the species that “definitely” or “likely” removed bait using track stations and cameras, 51% were taken by raccoons (Procyon lotor), 22% were taken by feral swine, and 20% were taken by collared peccaries (Tayassu tajacu). We found elevated serum IA values in 74% of trapped feral swine, 89% of raccoons, and 43% of opossums (Didelphis virginiana). Our oral delivery system was successful in marking a substantial proportion of feral swine. However, our observed removal rates suggest that the majority of the baits were taken by nontarget species and, therefore, unsuitable for most pharmaceutical applications in their current form.

SPECIES-SPECIFIC VISITATION AND REMOVAL OF BAITS FOR DELIVERY OF PHARMACEUTICALS TO FERAL SWINE

Within the domestic swine industry there is growing trepidation about the role feral swine (Sus scrofa) play in the maintenance and transmission of important swine diseases. Innovative disease management tools for feral swine are needed. We used field trials conducted in southern Texas from February to March 2006 to compare species-specific visitation and removal rates of fish-flavored and vegetable-flavored baits with and without commercially available raccoon (Procyon lotor) repellent (trial 1) and removal rates of baits deployed in a systematic and cluster arrangement (trial 2). During trial 1, 1) cumulative bait removal rates after four nights ranged from 93% to 98%; 2) bait removal rates by feral swine, raccoons, and collared peccaries (Pecari tajacu) did not differ by treatment; and 3) coyotes (Canis latrans) removed more fish-flavored baits without raccoon repellent and white-tailed deer removed more vegetable-flavored baits without raccoon repellent than expected. During trial 2, feral swine removed fish-flavored baits distributed in a cluster arrangement (eight baits within 5 m2) at a rate greater than expected. Our observed bait removal rates illustrate bait attractiveness to feral swine. However, the diverse assemblage of omnivores in the United States compared with Australia where the baits were manufactured adds complexity to the development of a feral swine-specific baiting system for pharmaceutical delivery.

Mammalian Visitation to Candidate Feral Swine Attractants

Abstract Few data exist regarding suitable feral swine (Sus scrofa) attractants in the United States. We compared species-specific visitation and contact rates of mammals to 11 candidate feral swine attractants at scent stations using motion-sensing digital photography to identify promising attractants. We found feral swine had greater visitation rates to apple and strawberry stations than to control stations. We recommend managers consider using strawberry attractants for feral swine-specific applications. If, however, a general feral swine attractant is needed, then apple, berry, or caramel attractants may perform well.

Feral Swine Behavior Relative to Aerial Gunning in Southern Texas

Abstract Feral swine (Sus scrofa) impact resources through their destructive feeding behavior, competition with native wildlife, and impacts to domestic animal agriculture. We studied aerial gunning on feral swine to determine if aerial gunning altered home range and core area sizes, distances between home range centroids, and distances moved by surviving individuals. We collected data before, during, and after aerial gunning in southern Texas. Using Global Positioning System collars deployed on 25 adult feral swine at 2 study sites, we found home range and core area sizes did not differ before and after aerial gunning. However, feral swine moved at a greater rate during the aerial gunning phase than during the before and after periods. We concluded that aerial gunning had only minor effects on the behavior of surviving swine and that this removal method should be considered a viable tool in contingency planning for a foreign animal disease outbreak.

Efficacy of the Boar-Operated-System to deliver baits to feral swine

Feral swine (Sus scrofa) pose a significant disease threat to livestock and humans. Emerging technologies to reduce feral swine disease transmission risks include fertility control, vaccination, and toxicants. However, for these technologies to be appropriate for field application, a feral swine-specific oral delivery system is needed. We used two field trials to generate information related to appropriate field application of the Boar-Operated-System (BOS™), an oral delivery system designed to provide bait access only to feral swine. Our objectives were to determine whether pre-baiting BOS™ units increased bait removal and to evaluate the proportion of feral swine and non-target animals that ingest baits designed to deliver pharmaceuticals through the BOS™. During both trials we used baits housed within 10 BOS™ units. We monitored wildlife visitation, bait removal, and ingestion using motion sensing digital photography and baits containing the bait marker tetracycline hydrochloride (TH). During trial 1 we found three of five pre-baited BOS™ units were used by feral swine only. Additionally, we found the five BOS™ units that were not pre-baited were not used by feral swine or non-target wildlife. During trial 2 we determined bait removal from the BOS™ to be reduced by only 10% for feral swine when activated, whereas bait removal from the BOS™ by all other wildlife was reduced by 100% when activated. We captured 81 feral swine and 23 raccoons and found 90% and 13% to have TH-marked teeth, respectively. With minor modifications, the BOS™ should be considered a valuable tool to be used in feral swine disease management in conjunction with existing technologies.

Evaluation of Fences for Containing Feral Swine under Simulated Depopulation Conditions

ABSTRACT Populations of feral swine (Sus scrofa) are estimated to include >2 million animals in the state of Texas, USA, alone. Feral swine damage to property, crops, and livestock exceeds

Strawberry‐Flavored Baits for Pharmaceutical Delivery to Feral Swine

50 million annually. These figures do not include the increased risks and costs associated with the potential for feral swine to spread disease to domestic livestock. Thus, effective bio-security measures will be needed to quickly isolate affected feral swine populations during disease outbreaks. We evaluated enclosures built of 0.86-m-tall traditional hog panels for containing feral swine during 35 trials, each involving 6 recently caught animals exposed to increasing levels of motivation. During trials, fences were 97% successful when enclosures were entered by humans for maintenance purposes; 83% effective when pursued by walking humans discharging paintball projectors; and in limited testing, 100% successful when pursued and removed by gunners in a helicopter. In addition to being effective in containing feral swine, enclosures constructed of hog panels required simple hand tools, took <5 min/m to erect, and were inexpensive (

Promiscuous mating in feral pigs (Sus scrofa) from Texas, USA

5.73/m excluding labor) relative to other fencing options. As such, hog-panel fences are suitable for use by state and federal agencies for rapid deployment in disease response situations, but also exhibit utility for general control of other types of damage associated with feral swine.

Impact of baiting on feral swine behavior in the presence of culling activities.

Abstract More effective methods to control feral swine (Sus scrofa) damage are needed. We evaluated 8 oral delivery systems designed to deliver pharmaceuticals to feral swine on 2 properties in southern Texas, USA. We used modified PIGOUT® feral pig bait (Animal Control Technologies Australia P/L, Somerton, Victoria, Australia) throughout our trials to compare species-specific visitation and removal rates. Given our consistent finding of high nontarget removal of baits intended for feral swine, we question whether a swine-specific oral delivery system exists for this region.

Efficacy of ERL-4221 as an ovotoxin for feral pigs (Sus scrofa).

Context Feral pigs represent a significant threat to agriculture and ecosystems and are disease reservoirs for pathogens affecting humans, livestock and other wildlife. Information on the behavioural ecology of feral pigs might increase the efficiency and effectiveness of management strategies. Aims We assessed the frequency of promiscuous mating in relation to oestrous synchrony in feral pigs from southern Texas, USA, an agroecosystem with a widespread and well established population of feral pigs. An association between multiple paternity of single litters and synchrony of oestrous may indicate alternative mating strategies, such as mate-guarding. Methods We collected gravid sows at nine sites in southern Texas during 2005–07. We used a panel of DNA microsatellite markers to estimate frequency of multiple paternity and the distribution of male mating among litters of feral pigs. Conception dates were determined by fitting average fetal crown–rump measurements within litters to expected fetal development relative to gestation time. Key results We found evidence of multiple paternity in 21 of 64 litters (33%) from seven of nine sites sampled. Synchrony of oestrous did not influence promiscuous mating, as we found multiple paternity at sites with synchronous and asynchronous oestrous. Males sired from 8 to 11 offspring at three sites where >10 litters were sampled. Mean litter size (5.4) was less than the best-fit value for the number of offspring, indicating that some males sired offspring with ≥ 2 females. Key conclusions Feral pigs in Texas appear to be promiscuous under a range of demographic conditions, unlike wild boar and feral pigs in other regions. The ecological and behavioural factors affecting multiple paternity are not clear, but may include male–male competition, harassment avoidance, genetic benefits for offspring, response to macro-habitat conditions, or selection. Implications A high incidence of sexual contact among individuals may increase the opportunity for diseases transmitted by oral or venereal routes, such as swine brucellosis and pseudorabies. In addition, fertility-control methods targeting males only are likely to be inefficient if female promiscuity is high; methods targeting females or both sexes jointly may be more effective.