Hunters versus hunted: New perspectives on the energetic costs of survival at the top of the food chain

The pervasive presence of human activities on land and the seas has toppled the top-of-the-food-chain position of many apex predators. Mammalian carnivores such as lions, wolves, polar bears and even narwhals are suddenly experiencing a downgrading from acting as ultimate hunters to being hunted. In this review, we investigated how changing from hunter to hunted altered the energy expended with each role, and ultimately the cost of survival during peak performance. Both terrestrial and marine mammals doubled the amount of energy they expended when threatened compared to when they acted as hunters. These costs will ultimately result in ecological consequences, especially as the duration and frequency of threats to wild species continue to grow and cumulative energetic costs become more apparent. Greater attention to the specific energy demands of apex predators is warranted and will allow for conservation strategies to be based on how these critical species were originally built.