Stable isotope signatures of large herbivore foraging habitats across Europe.

We investigated how do environmental and climatic factors, but also management, affect the carbon (δ13C) and nitrogen (δ15N) stable isotope composition in bone collagen of the two largest contemporary herbivores: European bison (Bison bonasus) and moose (Alces alces) across Europe. We also analysed how different scenarios of population recovery- reintroduction in bison and natural recovery in moose influenced feeding habitats and diet of these two species and compared isotopic signatures of modern populations of bison and moose (living in human-altered landscapes) with those occurring in early Holocene. We found that δ13C of modern bison and moose decreased with increasing forest cover. Decreasing forest cover, increasing mean annual temperature and feeding on farm crops caused an increase in δ15N in bison, while no factor significantly affected δ15N in moose. We showed significant differences in δ13C and δ15N among modern bison populations, in contrast to moose populations. Variation in both isotopes in bison resulted from inter-population differences, while in moose it was mainly an effect of intra-population variation. Almost all modern bison populations differed in δ13C and δ15N from early Holocene bison. Such differences were not observed in moose. It indicates refugee status of European bison. Our results yielded evidence that habitat structure, management and a different history of population recovery have a strong influence on foraging behaviour of large herbivores reflected in stable isotope signatures. Influence of forest structure on carbon isotope signatures of studied herbivores supports the "canopy effect" hypothesis.