Hunters versus Hunted: New perspectives on the physiological costs of survival at the top of the food chain

Global biotic and abiotic threats,particularly from pervasive human activities, are progressively pushing large, apex carnivorous mammals into the functional role of mesopredator. Hunters are now becoming the hunted. Despite marked impacts on these animals and the ecosystems in which they live, little is known about the physiological repercussions of this role downgrading from ultimate to penultimate predator.
Here we examine how such ecological role reversals alter the physiological processes associated with energy expenditure, and ultimately the cost of survival during peak performance.
Taxonomic group, preferred habitat, and domestication affected the capacity of the oxygen pathway to support high levels of aerobic performance by carnivorous mammals. Fear responses associated with anthropogenic threats also impacted aerobic capacity.  
Allometric trends for three energetic metrics (maximum oxygen consumption, field metabolic rates, and the cost per stride or step), showed di...