Wildlife and livestock use of extensive farm resources in South Central Spain: implications for disease transmission

Abstract

The interactions of extensively farmed livestock with wild ungulates contribute to the transmission and maintenance of, among other diseases, tuberculosis (TB) at the interface in South Central Spain (SCS), where farming typically occurs close to wildlife habitats. The aim of this paper is to describe (i) the use of extensive farm resources by wildlife and livestock and (ii) the factors involved. Camera traps (CTs) were placed at a priori risk points (n = 149 points, 2145 CT days) for interspecies interactions: water points, buildings, food points, and acorn fields (which also provide rich pasture), on 11 representative extensive beef cattle (n = 6) and Iberian pig (n = 5) farms. The use of extensive farm resources by wild ungulates was frequent and widespread throughout the study area (over 50 % of daily presence per farm of either wild boar Sus scrofa or red deer Cervus elaphus). This presence increased when there was a high abundance of wild ungulates on nearby hunting estates. No direct interactions were detected, and livestock and wild ungulates partitioned resource use temporally, signifying that the interaction was mainly indirect. The wild species that used all farm resources with by far the most frequency was red deer, although its presence decreased markedly when far from woodland edges. The presence of cattle was positively associated with that of wild boar at all the CTs and specifically with red deer at water points and in acorn fields. Pig presence was negatively associated with that of wild boar, suggesting the existence of competence-mediated avoidance. We propose that interactions at the wildlife-livestock interfaces could be reduced by carrying out specific actions adapted to Mediterranean conditions and farm management: removing and segregating access to risky water points, the wise management of grazing in space and time, and protecting food-rich pasture plots and woodland edges by means of fencing, which is particularly interesting as regards attempting to prevent red deer from accessing areas occupied by livestock and vice versa. Biosecurity programs must be farm-specific, and the effectiveness, costs, and practical value of interventions should be adaptively evaluated in the field in future research.