Emergence of a novel interaction between brown bear and cicada due to anthropogenic habitat modification

Abstract

Novel species interactions have generally emerged in ecosystems that are highly modified by human activities. Anthropogenic habitat modification, such as afforestation, is one possible driver of novel species interactions; however, empirical evidence remains scarce. In this study, we show that a novel predator-prey interaction between the brown bear (Ursus arctos) and nymphs of a cicada species (Lyristes bihamatus) is generated by anthropogenic habitat modification. We evaluated the frequency of brown bear predation on cicada nymphs and the density of cicada nymphs between natural forests and plantations, which are a typical type of human-modified habitat. We found that brown bear predation on cicada nymphs occurred only in the plantations. The density of cicada nymphs in the plantations was significantly higher than in the natural forest. Our results indicate that the plantation leads to the emergence of the bear-cicada interaction due to increasing the density of cicada nymphs. The study draws attention to the overlooked effects of anthropogenic habitat modification on species interactions.