No abstract

Reintroductions are often used for reestablishment of animal populations. The choice of age‐class of released individuals, however, is often arbitrary or based on expediency. We developed a demographic model that predicts the relative efficiency of releasing juveniles or adults for a given life cycle. The model accounts for possible reduction of survival and fertility of released adults. It also incorporates demographic and environmental stochasticity to compare release strategies of varying duration and number of releases. We applied the model to the case of reintroduction of Griffon Vultures (Gyps fulvus) in southern France, for which accurate monitoring allowed us to estimate demographic rates and consequences of releases. Overall, for Griffon Vultures, it is more efficient to release adults than juveniles, despite the observed reduction of demographic parameters following release. This approach could be used for the reintroduction of other species.

Feeding stations are commonly used to sustain conservation programs of scavengers but their impact on behaviour is still debated. They increase the temporal and spatial predictability of food resources while scavengers have supposedly evolved to search for unpredictable resources. In the Grands Causses (France), a reintroduced population of Griffon vultures Gyps fulvus can find carcasses at three types of sites: 1. “light feeding stations”, where farmers can drop carcasses at their farm (spatially predictable), 2. “heavy feeding stations”, where carcasses from nearby farms are concentrated (spatially and temporally predictable) and 3. open grasslands, where resources are randomly distributed (unpredictable). The impact of feeding stations on vulture’s foraging behaviour was investigated using 28 GPS-tracked vultures. The average home range size was maximal in spring (1272±752 km2) and minimal in winter (473±237 km2) and was highly variable among individuals. Analyses of home range characteristics and feeding habitat selection via compositional analysis showed that feeding stations were always preferred compared to the rest of the habitat where vultures can find unpredictable resources. Feeding stations were particularly used when resources were scarce (summer) or when flight conditions were poor (winter), limiting long-ranging movements. However, when flight conditions were optimal, home ranges also encompassed large areas of grassland where vultures could find unpredictable resources, suggesting that vultures did not lose their natural ability to forage on unpredictable resources, even when feeding stations were available. However during seasons when food abundance and flight conditions were not limited, vultures seemed to favour light over heavy feeding stations, probably because of the reduced intraspecific competition and a pattern closer to the natural dispersion of resources in the landscape. Light feeding stations are interesting tools for managing food resources, but don’t prevent vultures to feed at other places with possibly high risk of intoxication (poison).