The trophic pyramid revisited: most animal classes have more predator than herbivore species

Abstract

According to the trophic pyramid, a large array of herbivores (primary consumers) feed an increasingly narrower array of predators, from secondary consumers to top predators. However, the partitioning between herbivory and predation across the animal kingdom has not yet been tested at the global scale. Here, we use a survey of 33,762 animal species across ten major taxonomic groups (five vertebrates and five invertebrates) to partition food sources at the class and phylum levels. We use this partitioning, together with class-level biomass estimates, to create a global trophic pyramid of biomass. We show that: (1) the diet of eight of the ten groups of animals is dominated by prey rather than plants, accounting for 64-99% of the diet mass; (2) collectively across the terrestrial and marine environments, secondary consumers (invertivores; [~]1200 Mt C) have higher biomass than primary consumers (herbivores; [~]500 Mt C); (3) the two major exceptions, feeding mostly on plants, are mammals and insects; the latter form the major food source for terrestrial animals. For animal species in most classes, plants are not a food source, but rather invertebrates, mostly arthropods. Secondary consumers (invertivores) link primary consumers and top predators, and are hence pivotal to almost all food-webs.