Researchers examine the relationship of predator mass and energy expenditure in capturing prey of varying sizes and reveal how this relationship might have led to the extinction of large carnivores in the past.
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.
The authors also note that the largest terrestrial non-mammalian predators, such as Giganotosaurus and Tyrannosaurus, may have achieved their massive size by having a lower metabolic rate. Indeed, previous estimates of total metabolic rate for these species are similar to those of a mammal weighing about a ton.
Carnivores at the upper limits of body mass would have been heavily reliant on abundant large prey to both minimize energy expenditure and maintain high rates of energy intake. Slight environmental perturbations, man-made or otherwise, leading to lower prey availability, could readily upset this energy balance. It may have also contributed to the extinction of the largest carnivores and explain why the largest modern mammalian carnivores are so rare and vulnerable today.