Data from: Tracking ungulate diet: Comparing observational and DNA metabarcoding tools

Large mammalian herbivores (LMH) are abundant in grazing ecosystems and
play a pivotal role in shaping vegetation characteristics. However,
accurately determining their diets through traditional methods, such as
direct observations, remains challenging, particularly in natural
communities and mixed-species grazing systems. Recent studies have shown
that DNA metabarcoding can effectively identify the plant composition in
LMH diets as well as the plant-dwelling arthropods (PDA) incidentally
ingested by LMH while grazing. Given the high specificity of herbivorous
insects to their host plant, we hypothesize that DNA metabarcoding of
arthropods ingested by LMH could offer valuable insights into their
feeding preferences. The goal of this study is to evaluate the accuracy of
plant and arthropod DNA metabarcoding methods in identifying the diets of
sheep and cattle and to compare their performance with direct observations
and known dietary patterns from the literature. To test this, we collected
fecal samples from sheep and cattle grazing in the northeast Asian
grasslands. We amplified arthropod DNA using COI mitochondrial markers and
plant DNA using ITS1 markers, followed by Illumina sequencing.
Additionally, we conducted field observations to identify plants grazed by
sheep and cattle. The DNA metabarcoding methods provided a comprehensive
view of the LMH diet. Both DNA metabarcoding methods successfully detected
dietary differences between sheep and cattle, with sheep primarily
consuming nutrient-rich forbs and cattle predominantly grazing on Poaceae,
consistent with known foraging behaviors. While the constant presence of
arthropods across multiple samples suggests that DNA of ingested
arthropods could provide complementary information regarding LMH foraging
behavior, we found such to be rather limited. However, our findings
confirm that plant DNA metabarcoding is a reliable and accurate method for
identifying LMH diets.