Direct consumptive interactions between mammalian herbivores and plant-dwelling invertebrates: prevalence, significance, and prospectus

Mammalian herbivores induce changes in the chemical composition, phenology, distribution, and abundance of the plants they feed on. Consequently, invertebrate herbivores (predominantly insects) that depend on those plants, and the predators and parasitoids that are associated with them, may be affected. This plant-mediated indirect interaction between mammals and invertebrates has been extensively studied, but mammalian herbivores may also directly affect plant-dwelling invertebrates (PDI) by incidentally ingesting them while feeding. The ubiquity and small size of PDI render them highly susceptible to incidental ingestion, but as common as this interaction may intuitively seem, very little is known about its prevalence and ecological consequences. Nevertheless, cases of incidental ingestion of PDI and associated adaptations for avoiding it that have been sporadically documented in several invertebrate groups and life stages allow us to carefully extrapolate and conclude that it should be common in nature. Incidental ingestion may, therefore, bear significant consequences for PDI, but it may also affect the mammalian herbivores and the shared plants. Future research on incidental ingestion of PDI would have to overcome several technical difficulties to gain better insight into this understudied ecological interaction.