An expanded predator-prey community model, its application to dinosaur coummunities, and selection for giant body size in sauropods

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Pictures of theropods preying on large sauropods dominate the public conception of the dinosaur ecosystem, but modern predator-prey size dynamics that would corroborate this view remain under debate. Although it is well known that relative energy requirements (per unit body mass) decrease with increasing body mass, a corresponding decrease in the prey size of predators of increasing size is rarely documented. Instead, relative prey size appears to either increase with predator body size or remain constant. Community foodwebs are usually constructed in a triangular way, with predators of increasing body mass feeding on the whole range of prey below their own body size. However, data for large mammalian terrestrial predators indicate otherwise. We will expand current models of predator-prey size relationships for terrestrial vertebrates, basing a physiological model on first principles concerning time-energy budgets, densities and encounter rates, and prey vulnerability as determined by agility and locomotion, to investigate a size threshold above and below which prey is no longer acceptable for a predator. This threshold will be used to expand a predator-prey community model beyond the usual ‘triangular’ approach. Models will be validated by physiological and community datasets. The results will be used for a reconstruction of dinosaur ecosystems in terms of predator-prey relationships that are based on physiological assumptions (such as to agility and metabolism). The reconstructions will also include scenarios of prey productivity and scenarios that trace the ontogenetic susceptibility of sauropods to predators, testing the effect of their fast growth rates and adult gigantism.