Herbivore Impact on Eurasian Landscape Ecology

Herbivory is a major natural process in shaping habitats. The different herbivore species occupy different ecological niches and differ in the influence they exert. Large herbivores are thought to have had a considerable impact on the ecosystem. Some species formerly wide spread throughout Eurasia like the aurochs (Bos primigenius) and the wild horse (Equus ferus) are now extinct but their ecological role in the formation of terrestrial habitats of this part of the world is regarded crucial. Under interglacial conditions, they thus created richly structured landscapes comprising a mosaic of open habitats and forests and where therefore umbrella species that provided habitats for others.

Like elephants and rhinos, all specialised grazers are extinct in the wild in large areas of the northern half of Eurasia. In Europe steppe rhino (Stephanorhinus hemitoechus), wild ass (Equus hydruntinus), horse and aurochs are missing.

In late Pleistocene and early Holocene times there was obviously only one species of caballine horse (Equus ferus) in Eurasia. About 15.000 years ago, Equus ferus had a continuous range from Iberia in the west to Beringia and Alaska in the east. For thousand of years the wild horse was an important game species for man, but it became progressively rarer during the Holocene. The last indisputably undomesticated horses belonging to the subspecies Equus ferus przewalskii were seen in Mongolia in 1968. After the initial domestication of horses at the earliest about 3.500 B. C. domestic horses (Equus ferus f. caballus) reached most parts of Eurasia after the wild horses were already extinct, and in part feral populations later took over the vacant niches.

Aurochsen are found in Europe since the middle Pleistocene. They were widespread over most of the northern hemisphere with the exception of North America. The species reached its highest population densities in Europe in the early Holocene, at a time, when other large herbivores species were already extinct. The subsequent decline was hypothesised to be the result of habitat loss, hunting and competition with domesticated cattle; that was introduced to Central Europe by farming communities from 4.500 B. C. onwards. The wild aurochs went extinct in Western Europe and large parts of Central Europe between 1.000 and 1.400 A. D.

The resource partitioning of wild and domesticated cattle during the long period of co-existence is currently being investigated in southern Scandinavian Holocene populations. If we want to understand the process of landscape formation, vegetation structure and resource availability as an equilibrium influenced by major biotic actors, the better understanding of the ecological position of the umbrella species in Eurasian ecosystems is the major focus of this research endeavour.