Major decline in marine and terrestrial animal consumption by brown bears (Ursus arctos).

Jun Matsubayashi,Ichiro Tayasu,Kyoko Kobayashi,Junko O Morimoto,Futoshi Nakamura,Osamu Takahashi,Miyuki Nakajima,Tsutomu Mano

doi:10.1038/srep09203

Abstract

Human activities have had the strongest impacts on natural ecosystems since the last glacial period, including the alteration of interspecific relationships such as food webs. In this paper, we present a historical record of major alterations of trophic structure by revealing millennium-scale dietary shifts of brown bears (Ursus arctos) on the Hokkaido islands, Japan, using carbon, nitrogen, and sulfur stable isotope analysis. Dietary analysis of brown bears revealed that salmon consumption by bears in the eastern region of Hokkaido significantly decreased from 19% to 8%. In addition, consumption of terrestrial animals decreased from 56% to 5% in western region, and 64% to 8% in eastern region. These dietary shifts are likely to have occurred in the last approximately 100–200 years, which coincides with the beginning of modernisation in this region. Our results suggest that human activities have caused an alteration in the trophic structure of brown bears in the Hokkaido islands. This alteration includes a major decline in the marine-terrestrial linkage in eastern region, and a loss of indirect-interactions between bears and wolves, because the interactions potentially enhanced deer predation by brown bears.

Highlights

Human activities have had the strongest impacts on natural ecosystems since the last glacial period, including the alteration of interspecific relationships such as food webs
Temporal shifts in the d34S values were only found in the western area, which can be attributed to differences in feeding habits between Periods
Our stable isotope analysis illustrated that a major decline in animal consumption by brown bears occurred from Period 1 to Period 3 in the eastern and western area of Hokkaido (Fig. 4)

Summary

Introduction

Human activities have had the strongest impacts on natural ecosystems since the last glacial period, including the alteration of interspecific relationships such as food webs. We present a historical record of major alterations of trophic structure by revealing millennium-scale dietary shifts of brown bears (Ursus arctos) on the Hokkaido islands, Japan, using carbon, nitrogen, and sulfur stable isotope analysis. Our results suggest that human activities have caused an alteration in the trophic structure of brown bears in the Hokkaido islands This alteration includes a major decline in the marine-terrestrial linkage in eastern region, and a loss of indirect-interactions between bears and wolves, because the interactions potentially enhanced deer predation by brown bears. We investigated the millennium-scale diet changes in brown bears in the Hokkaido islands, Japan, using carbon, nitrogen and sulfur stable isotope analysis, and we assessed the impacts of human development on the food web structures of these terrestrial ecosystems. We measured the stable isotope values of potential diet items of Hokkaido brown bears to assist in the interpretation of the isotopic values in brown bears

Methods

Results

Conclusion