GPS and Accelerometer Data Reveal the Importance of Extensive Livestock Grazing in the Trophic Ecology of Griffon Vultures in Northern Spain

The Eurasian Griffon Vulture (Gyps fulvus) is the most abundant obligate scavenger in Europe. It depends on wild and domestic carcasses whose availability and location are relatively unpredictable in terms of space and time, but also on predictable sources of anthropogenic origin. In this study, satellite and accelerometer data from 10 adult individuals captured in the Basque Country (N Spain) were analysed with the aims of identifying feeding sites and determining the types of resources used. The annual cycle of the species was subdivided into three phases: pre-laying and incubation (December–March), rearing (April–July) and post-rearing (August–November). Our results showed that 64% of trophic resources were consumed in mountain pastures and on extensive or semi-extensive livestock farms, highlighting the importance of these farming systems for the species in the study area. However, 36% of the resources were exploited in more predictable anthropic environments, such as landfills and supplementary feeding stations and, to a much lesser extent, intensive farms. Individual variability was detected in terms of trophic behaviour. On semi-extensive farms, the most consumed carcasses were sheep (48%) and horses (37%), while on intensive farms, it was pigs (81%). During the pre-laying and incubation phase, feeding events detected in landfills were reduced, with vultures focusing on resources close to the colony. We observed that the population studied differed from other Spanish populations in its greater use of trophic resources from extensive and semi-extensive livestock farms, as expected from their spatial-temporal distribution and local availability.