Can incidental ingestion of plant-dwelling insects nutritionally benefit ungulates?

Abstract The diet of ungulates is often characterized by low protein levels and the presence of indigestible and defensive compounds. It also often lacks micronutrients (vitamins and minerals) essential for growth, health and reproduction. Ungulates select rich plant organs to compensate for nutrient shortages and may consume soil, faeces and even bones. It is common for ungulates to incidentally ingest plant-dwelling insects (PDI) while feeding. It is well known that insects contain protein and essential nutrients that can feed livestock, potentially replacing conventional feed. Based on this, we propose the ‘nutritional benefit of incidental ingestion’ hypothesis, suggesting that ungulates may nutritionally benefit from ingesting PDI while foraging. Based on evidence from the literature on PDI ingestion by ungulates and on the nutritional properties of different insects, we discuss how and whether the ingestion of PDI while foraging might improve the nutrient balance of ungulates and recommend a set of controlled experiments to test it. We provide a new and unfamiliar dimension of nutritional ecology, which is relevant to various grazing ecosystems. We propose to modify “trivial” food web structures, as direct trophic interactions between ungulates and PDI may hold greater significance for ungulate performance and behaviour.