The Cost of Carnivory

A recent open-access peer reviewed entry at PLoS, the authors review biomass of carnivores. The review yields a predictive model of mass to energy needs and projects size estimates on carnivores. This model may be beneficial in predictive examination of fossil finds, as well as new carnivores (as discovered) to project the expected maximum weight of the species. It can also be used as a litmus to determining weight estimates associated to those reports of large mammalian like creatures.

Craig Heinselman
Peterborough, NH


The Cost of Carnivory

C. Carbonem A. Teacher, J.M. Rowcliffe
PLoS Biology, February 2007, Volume 5, Issue 2

Given these energetic constraints, we predict a maximum mass for a mammalian carnivore at 1,100 kg. Among extant species, the polar bear is the largest carnivore with the largest recorded individual weighing 1,002 kg However, at least four carnivore species with a very large average body mass are known to occur in the fossil record: the short-faced bear Arctodus simus, estimated at 800–1,000 kg; the North American lion Panthera atrox and the South American sabercat Smilodon populator both around 500 kg; and Megistotherium osteothlastes (880 kg) While there is conflicting evidence about whether some of these species were pure carnivores (e.g., short-faced bear ), ancient bears had morphological similarities to the carnivorous polar bear. Thus, we believe that these species represent a possible upper limit to mammalian carnivore body size and this provides support for our model prediction. This prediction, however, is based on mammalian metabolic rates and costs of transport. Were we to assume lower metabolic rates (e.g., as in reptiles), we would predict a larger maximum mass. The largest terrestrial predators, such as Giganotosaurus and Tyrannosaurs, may have achieved their massive size by having a lower metabolic rate, and it is interesting, in this context, that estimates of total metabolic rate for these species are similar to those of a mammal weighing about a ton
Our analysis provides a broad perspective on energy and time budgets in mammalian terrestrial carnivores and provides insights into carnivore conservation and evolution, helping us to understand the vulnerability of large carnivores to historical and future extinctions. Among extant carnivores, the largest species are particularly vulnerable to human threat processes and have been shown to have higher rates of extinction in the fossil record than smaller species, even prior to the evolution of man . At the upper limits of body mass, an extremely high-prey biomass would be required to both minimize energy expenditure and maintain high rates of energy intake. Slight environmental perturbations, anthropogenic or otherwise, leading to lower prey availability, could readily upset this energy balance.