Grazing by sheep Ovis aries reduces island populations of water voles Arvicola amphibius

• Published in: Fauna norvegica
• Main Author: Karl Frafjord
• Format: Article in Journal/Newspaper
• Language: English
• Published: Norwegian University of Science and Technology 2014
• Subjects: competition; ecosystem; grazing; islands; sheep; Mammalia; Zoology; QL1-991; Norway; Solvær; Northern Norway
• Online Access: https://doi.org/10.5324/fn.v34i0.1673; https://doaj.org/article/2aeb62eeff3b46c392b7a59a7eb13e8e

The population of water voles Arvicola amphibius was surveyed on 21 islands in the Solvær archipelago, northern Norway, in August 2012; 11 islands with semi-wild domestic sheep Ovis aries and 10 islands without sheep. Signs from water voles are very easy to detect and were used as a measure of the population (on a scale 0-10), and the numbers of sheep were counted. The ranking of signs on islands with and without sheep was compared, and a significant difference was found. Islands with sheep had, with one exception, only very small and fragmented populations of water voles, the one exception being a fairly large Carex swamp that was not grazed by the sheep and where a moderate-sized population of voles was found. Islands without sheep had much larger populations of water voles, giving a ranking about four times higher. One reason for the devastating effect of sheep on water voles is probably the fact that the sheep are living year-round on these islands with no supplemental food.