Rarefaction
We used rarefaction to infer whether the sampling depths were sufficient to describe the full prey composition (i.e. zOTU richness). In theory, when rarefaction curves approximate a plateau, only a few novel zOTUs will be found with increased sequencing depth, thus indicating that the samples represent the full diversity of prey. The datasets all displayed plateau-like curves (Fig. 1), but curves of from the full sequencing run (pilot full, full) were arguably less steep. The average slope (i.e. zOTU discovery rate) of samples in the full dataset were smaller (0.0045, i.e. 4.5 new prey zOTUs per 1000 reads, Fig. 1c) as opposed to 0.0103 for the pilot dataset (i.e. 10.3 new zOTUs per 1000 reads, Fig. 1a).