In our model, predatory carnivores are divided into two basic hunting groups (following ): those that feed on small prey (invertebrates 10 kg). In order to estimate the scaling of carnivore energy budgets, we develop a simple model that incorporates both the scaling of costs associated with body mass and the differences in time and energy budgets associated with hunting strategy. Our approach provides a framework to understand adjustments in carnivore energy budgets and provides insights into the evolution of body size in this diverse group. In this paper, we develop a simple model to examine adjustments in carnivore energetics in relation to predator and prey size and compare the model predictions with observed estimates of field metabolic rates (FMR) and intake rates. Thus far, however, there has been no general framework to interpret adjustments in carnivore energy budgets associated with changes in body mass and hunting strategy. Large carnivores, however, with their large prey, have higher hunting costs, with long high-speed chases and high costs of capture and killing. Small-prey-feeding carnivores appear to have relatively low hunting costs-searching and pursuit can occur at walking pace and the capture and killing phases are often very brief. Smaller species (15вЂ“20 kg), on the other hand, specialize in large-vertebrate prey near their own mass. Carnivores also exhibit different hunting strategies in relation to their mass. Consequently, carnivores are some of the widest ranging terrestrial mammals for their size, and this affects overall energy budgets. The largest prey species themselves, can be unpredictable in space and time, widely dispersed, and rare.

Many species in the Order Carnivora, for example, are at a high trophic level, with their population biomass representing only a small fraction of that of their prey. Predators face severe energetic constraints that affect many aspects of their ecology and evolution.

This study suggests that those extremely large carnivores would have been heavily reliant on abundant large prey, helping to explain why the largest modern mammalian carnivores are rare and vulnerable to extinction. The largest existing carnivore, the polar bear, is only around half a ton, while the largest known extinct carnivores, such as the short-faced bear, weighed around one ton. Thus, mammalian carnivores are relatively small compared with the largest extinct terrestrial herbivorous mammals, such as the Indricothere, which weighed around 15 tons. Analyzing the balance between energy intake and expenditure across a range of species, we predict that mammalian carnivores should have a maximum body mass of one ton. While carnivores around the size of a lynx or larger can obtain higher net energy intake by switching to relatively large prey, the difficulty of catching and subduing these animals means that a large-prey specialist would expend twice as much energy as a small-prey specialist of equivalent body size. Our approach provides a framework for understanding carnivore energetics, size, and extinction dynamics.Д¬arnivores fall into two dietary groups based on the energetic requirements of their feeding strategies: small-bodied species, which feed mostly on prey smaller than themselves, and large-bodied species, which prefer prey around their own size. Given predictions of expenditure and estimates of intake, we predict a maximum carnivore mass of approximately a ton, consistent with the largest extinct species. This suggests that carnivores at the upper limits of each group are constrained by intake and adopt energy conserving strategies to counter this. However, when each dietary group is considered individually they both display a shallower scaling. Across all species, energy expenditure and intake both follow a three-fourths scaling with body mass. However, because it requires more energy to pursue and subdue large prey, this leads to a 2-fold step increase in energy expenditure, as well as increased intake. We show that the transition from small to large prey can be predicted by the maximization of net energy gain larger carnivores achieve a higher net gain rate by concentrating on large prey. We develop a model that predicts the mass-related energy budgets and limits of carnivore size within these groups. Mammalian carnivores fall into two broad dietary groups: smaller carnivores (20 kg) that specialize in feeding on large vertebrates.

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