Why are terrestrial predators smaller than elephants?

During evolution, terrestrial predators like lions or wolves have never been the same size as elephants. But if that is the case, they will become extinct because they cannot catch enough prey to meet their body's energy needs.

(Photo: nationalgeographic) "Mammals are not allowed to own a large body , " said Chris Carbone, an expert at the Animal Research Institute in London.

Carbone and colleagues read publications about the daily energy consumption of mammals. As expected, they found consumption increased with body size. If the body size doubled, their energy demand increased by 1.6 times.

Mammals are divided into two groups. Small sized animals (weighing about 15-20 kg) often eat rats, insects and smaller creatures. Meanwhile, larger ones, like tigers, polar bears, tend to hunt animals of similar or larger sizes.

" Austerity " strategy

The researchers also found that the largest large carnivores in both groups had difficulty providing enough energy for the body. Wolves (the largest species in the small group) and polar bears, lions (the largest of the large group) are forced to invest most of their time in resting and moving slowly to maintain energy. With their large bodies, their " charging " speed and energy consumption tend to be slower than those of medium and small carnivores.

Ecologist James Brown (Photo: unm.edu)

Small predators can still make their body size bigger by catching large prey, but big predators have no strategy to choose from, scientists concluded.

With that inference, Carbone's team predicted that predators could not provide enough energy for the body if their weight was greater than 1,000 kg. The fossil of a short-faced bear, considered the largest ever, weighs only nearly 1,000 kg. Polar bears, the largest mammal today, have not yet reached that weight.

The energy needs of the largest plant-eating dinosaurs that have ever appeared on the planet - such as T. rex - are only equivalent to a carnivore weighing 1,000 kg. The " limit threshold " for weight for marine species may be higher, because the food source here is much more abundant. The abundance of food in the oceans allows carnivorous mammals, such as whales, to reach larger sizes than terrestrial predators. That's the judgment of James Brown, an ecologist at the University of New Mexico (USA).

The " austerity " strategy in the consumption of energy of large terrestrial predators means that they face more risks than other species when habitat or climate change. That's why the largest terrestrial carnivores ever appeared on Earth are extinct, John Gittleman, an ecologist at the University of Georgia (USA), concluded.

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