Crop circles revealed spatio-temporal patterns of beaver foraging on cereal fields

Abstract

The surface of the Earth is increasingly dominated by human-modified ecosystems, and many wildlife species are adapting to live within agricultural landscapes. Crops offer a predictable and nutritious food source that may become an integral part of the diet of some wildlife species. Eurasian beavers (Castor fiber) are closely associated with forests and wetlands, but recolonizing their previous range following centuries of persecution, they settle into a highly anthropogenic landscape. We investigated spatial patterns of beaver foraging on cereals in southeastern-Norway, 2019 and 2020, as well as beaver movements in crop fields using GPS tags, 2010–2021. Beavers foraged mostly on wheat (Triticum aestivum), followed by oats (Avena sativa), barley (Hordeum sativum), and rye (Secale cereale). The probability that a beaver would forage on cereals decreased with the width of the forested buffer zone, and with increasing elevational gain from water. The extent of foraging increased while cereal plants ripened in early fall, and beavers removed larger areas when foraging further away from water. The extent of foraging varied among beaver territories, but we could not identify the cause of these differences. However, we found that beavers that moved extensively in crop fields also displayed an improved body condition. During late summer to early fall, cereals might provide a supplementary food source for this generalist and opportunistic species. As wildlife populations settle into agricultural land, crops might become a vital part of their diet, which requires research attention to reduce conflicts and improve our understanding of wildlife foraging ecology within anthropogenic landscapes.