Wolf response to two kinds of barriers in an agricultural habitat in Spain

Abstract

We examined the effect of two kinds of barriers on an expanding gray wolf, Canis lupus L., 1758, population in an agricultural habitat in north-central Spain. The barriers were (i) a four-lane fenced highway along a flat area without wildlife-crossing facilities, and (ii) the River Duero Artery (RDA), comprising the river itself (50–100 m wide) and several small infrastructures along it. From March 1997 to October 2001, all 4 radio-collared wolves living <15 km from the highway (1 adult territorial male, 1 territorial breeder female, 1 dispersing male, and 1 female in 3 periods of her life (territorial immature, disperser, and territorial breeder) crossed it on between 4% and 33% of 45–163 monitoring days via vehicle bridges. Moreover, 4 more highways that we monitored in areas without radio-collared wolves have not delayed expansion of the increasing wolf population, suggesting that these highways are not an important barrier for wolves in our study area. In contrast, only 3 of 8 wolves radio-collared <5 km from the RDA were detected crossing it, and 2 of those 3 started to cross it only after severe habitat disturbance; in addition, the RDA seems to have delayed wolf expansion for some 15 years, which suggests that it is a semipermeable barrier for wolves. We discuss the likely consequences of the RDA on the recovery of the Iberian wolf population.