Optimizing the baiting strategy for oral vaccine delivery to wild boar

Baits are a means of orally delivering toxicants, medicaments, or chemical markers to wild boar and feral pigs (Sus scrofa). We tested three bait types, the paraffin-feed-sugar-based IREC bait (green and colorant-free versions), a puffed leguminous bait with the same flavoring as the IREC bait (Flavor), and a plain puffed leguminous bait without flavoring (Plain). Baits were deployed in a fenced hunting estate with year-round feeding to assess bait type preference and study the effect of bait flavoring and coloring, pre-feeding, baiting device, and habituation on bait consumption and bait selectivity. Baits were deployed under heavy pavel stones, targeting adult wild boar, or in piglet-selective feeders. The main bait consumer was the wild boar (IREC 54%; Flavor 15%; Plain 16%) followed by azure-winged magpies (Cyanopica cooki; IREC 11%; Flavor 8%; Plain 17%). The most consumed bait was IREC (n = 164; 71%, mean 4.1 baits per site/day), followed by Flavor (102; 40%; 2.5) and Plain (70; 29%; 1.7). Pre-feeding increased bait consumption of all bait types (IREC 92%; Flavor 63%; Plain 40%). IREC baits were more consumed when deployed under stones (86%) than when deployed in piglet feeders (57%), while no difference between baiting devices was observed for Flavor and Plain baits. Birds preferred color-free baits (consumption ratio of 10% for color-free baits and 0% for green baits), while no other animal showed color preference. We suggest using green IREC-type baits, deployed after pre-baiting using species- and age-specific baiting devices.