Not only mosses: lemming winter diets as described by DNA metabarcoding

Abstract

The temporal dynamics of most tundra food webs are shaped by the cyclic population dynamics of lemmings. While processes during winter may be behind the recent disruptions of lemming cycles, lemming winter ecology is poorly known. We present here the first DNA metabarcoding data on the winter diet of Norwegian lemmings (Lemmus lemmus), based on feces collected after a winter of population increase. Prostrate willows, mosses, and graminoids dominated the species winter diet, indicating that the conventional idea of lemmings as moss‐specialists should be revised. The behavior of lemming‐plant models in theoretical studies is conditional on the assumptions of mosses being their main winter food item. As shrubs have been excluded from the framework of these models, incorporating them in future modeling studies should nuance our understanding on how plants affect lemmings. We also sampled diet of a few individuals found dead on top of the snow. These individuals had relatively empty stomachs and had, prior to death, relied heavily on mosses. This apparent lack of abundant good quality indicates spatial heterogeneity in local food availability during the population increase phase.