Baiting improves wild boar population size estimates by camera trapping

In the last decade, camera trapping has become a widespread technique for wildlife monitoring. Although baits or attractants are commonly used to increase the likelihood of encounter, this practice has been criticised because of the potential biases in the population estimations based on these records obtained by mark-recapture or mark-resight methods, and especially in relative abundance indices (RAI). For two consecutive years, we evaluated the impact of baiting on wild boar (Sus scrofa) population estimates in a protected area of northeast Spain. In particular, we compared the number of boars per independent events (the group size), the estimated population size and RAI between periods with and without baiting. Baiting increased mean group size estimation and the likelihood of an encounter leading to more precise wild boar population estimates. The RAI values both at baited and unbaited campaigns correlated significantly with mark-resight abundance estimates, suggesting that these indices could be used to evaluate the boar population changes.