European Bison as a Refugee Species? Evidence from Isotopic Data on Early Holocene Bison and Other Large Herbivores in Northern Europe

Abstract

According to the refugee species concept, increasing replacement of open steppe by forest cover after the last glacial period and human pressure had together forced European bison (Bison bonasus)—the largest extant terrestrial mammal of Europe—into forests as a refuge habitat. The consequent decreased fitness and population density led to the gradual extinction of the species. Understanding the pre-refugee ecology of the species may help its conservation management and ensure its long time survival. In view of this, we investigated the abundance of stable isotopes (δ13C and δ15N) in radiocarbon dated skeletal remains of European bison and other large herbivores—aurochs (Bos primigenius), moose (Alces alces), and reindeer (Rangifer tarandus)—from the Early Holocene of northern Europe to reconstruct their dietary habits and pattern of habitat use in conditions of low human influence. Carbon and nitrogen isotopic compositions in collagen of the ungulate species in northern central Europe during the Early Holocene showed significant differences in the habitat use and the diet of these herbivores. The values of the δ13C and δ15N isotopes reflected the use of open habitats by bison, with their diet intermediate between that of aurochs (grazer) and of moose (browser). Our results show that, despite the partial overlap in carbon and nitrogen isotopic values of some species, Early Holocene large ungulates avoided competition by selection of different habitats or different food sources within similar environments. Although Early Holocene bison and Late Pleistocene steppe bison utilized open habitats, their diets were significantly different, as reflected by their δ15N values. Additional isotopic analyses show that modern populations of European bison utilize much more forested habitats than Early Holocene bison, which supports the refugee status of the species.

Bondi Cave and the Middle-Upper Palaeolithic transition in western Georgia (south Caucasus)

“…The protocol follows that published in Bocherens et al (1997Bocherens et al ( , 2015. All samples were screened for nitrogen content (Bocherens et al, 2005) and only bones with more than 0.4% nitrogen were used for collagen extraction.…”

Past climate changes, population dynamics and the origin of Bison in Europe

“…B. bonasus has a relatively more massive rear quarter and shorter horns compared to B. priscus, which has longer and slightly curved horns and a smooth double-humped appearance [15,16]. B. priscus and B. bison (Linnaeus, 1758), both of which are grazers, have a lower head position than B. bonasus, which is a mixed feeder [18]. It is, however, very difficult to assign fossil bison bones to either species [2].…”

“…The wisent also almost went extinct at the beginning of the 20th century. Indeed, similar to other large herbivores, such as the aurochs, intensification of agriculture since the Neolithic period pushed the wisent into the forests of Eastern Europe [18], where it was strictly protected for several centuries as royal game [11]. During the First World War, however, a diminished population size followed by poaching led to its extinction in the wild [11].…”

Risk perception by endangered European bison Bison bonasus is context (condition) dependent

“…European bison were reintroduced to forest habitats after their extinction in the wild at the beginning of the twentieth century. They increasingly utilise open areas in the vicinity of forest habitats, especially in winter, to compensate for scarcity of graze within forest habitats due to the bisons' adaptations for open or mixed habitats and its hypothesised 'refugee' status in forests Bocherens et al 2015). This also reduces bison density at feeding sites and thereby reduces parasite loads (Radwan et al 2010;Pyziel et al 2011).…”