Abstract
Large mammalian herbivores influence grassland ecosystems through plant consumption, return of excreta and trampling, and by altering nutrient cycles and soil properties. These herbivore-mediated changes impact other animals in the habitat, particularly plant-dwelling arthropods. While plant-mediated effects of large mammalian herbivores on arthropod populations are well documented, direct effects, such as incidental ingestion of arthropods, remain understudied. Large mammalian herbivores incidentally ingest a variety of plant-dwelling arthropods; however, it remains unclear how this interaction is influenced by the dietary choices of different mammal species within the same habitat. Using a DNA metabarcoding analysis of fecal samples, we investigated the ingestion of plant-dwelling arthropods by sheep and cattle grazing in northeast Asian grasslands. Fecal samples were collected from replicated plots throughout the grazing season, including previously grazed and ungrazed plots. A COI marker was used to amplify arthropod DNA, followed by high-throughput sequencing. Results revealed that both sheep and cattle ingest a variety of plant-dwelling arthropods, including herbivores, parasitoids, and predators, with a high proportion of endophages (species developing in plant tissue). Significant differences were observed in ingestion between sheep and cattle-sheep (selective grazers) ingested a wider variety of plant-dwelling arthropods compared to cattle, whose diet consisted primarily of grasses, highlighting the impact of dietary choices on arthropod ingestion. Grazing regime influenced the ingestion of plant-dwelling arthropods in sheep, with differences observed between previously grazed and ungrazed plots. Our findings demonstrate that the ingestion of plant-dwelling arthropods by large mammalian herbivores is a dynamic and widespread phenomenon, varying across mammalian species and seasons.