Abundance of wild prey modulates consumption of supplementary food in the Iberian lynx

Food supplementation is increasingly used as a conservation tool. However, little is known about how much supplemental food is used by target populations or the degree to which the abundance of natural food affects the utilization of supplemental food. Long-term supplementation programmes could cause individuals to rely almost exclusively upon supplemental food and, consequently, lose some skills needed to forage efficiently on natural food. This may result in reduced fitness upon discontinuation of supplemental food. The Iberian lynx (Lynxpardinus) preys almost exclusively upon European wild rabbits (Oryctolagus cuniculus), and some populations are thought to be food limited. We quantified the contribution of supplemented domestic rabbits, whose guard hairs could be distinguished from hairs of wild rabbits, to the diet of the Iberian lynx. We also examined whether the consumption of domestic rabbits varied with the availability of wild rabbits, and with the duration of exposure to supplemental food. Domestic rabbits made up over 50% of the diet. Consumption of domestic rabbits decreased non-linearly as the relative abundance of wild rabbits increased; however, this pattern was true only above a threshold density of one wild rabbit km−1. Below this threshold, supplementation was apparently strictly necessary to retain Iberian lynx. The consumption of domestic rabbits did not increase with the length of the supplementation period. Lynx continued consuming wild rabbits proportionally to their abundance, suggesting lynx did not become dependent upon supplemental food. Understanding how the abundance of natural food modulates consumption of supplemental food may help to adjust supplementation schedules to food availability and to the needs of the target populations.