Humans as predators led to the extinction of woolly mammoths

Washington, July 3 (ANI): Life scientists have found what led to the extinction of woolly mammoths and other large mammals more than 10,000 years ago- entry of humans as predators.

Researchers have said that the same type of cascade of ecosystem disruption that is being caused today by the global decline of predators such as wolves, cougars and sharks, is what led to the extinction of large mammals like woolly mammoths.

Just like it is happening now, the cascading events then were originally triggered by human disruption of ecosystems, concluded a new study.

But around 15,000 years ago the problem was not the loss of a key predator, but the addition of one - human hunters with spears.

This mass extinction was caused by newly arrived humans tipping the balance of power and competing with major predators such as sabertooth cats, argued the authors of the new analysis.

An equilibrium that had survived for thousands of years was disrupted, perhaps explaining the loss of two-thirds of North America's large mammals during this period.

"We suggest that the arrival of humans to North America triggered a trophic cascade in which competition for the largest prey was intensified, ultimately causing the large non-human carnivores to decimate the large herbivores. When human hunters arrived on the scene, they provided new competition with these carnivores for the same prey," said Blaire Van Valkenburgh, UCLA professor of ecology and evolutionary biology and a co-author on the paper.

"The addition of humans was different from prior arrivals of new predators, such as lions, because humans were also omnivores and could live on plant foods if necessary. We think this may have triggered a sequential collapse not only in the large herbivores, but ultimately their predators as well. Importantly, humans had some other defenses against predation, such as fire, weapons and living in groups, so they were able to survive," he added.

"For decades, scientists have been debating the causes of this mass extinction, and the two theories with the most support are hunting pressures from the arrival of humans and climate change," said William Ripple, a professor of forest ecosystems and society at Oregon State University and lead author on the paper.

Researchers said that in the late Pleistocene, major predators dominated North America in an uneasy stability with a wide range of mammals: mammoths, mastodons, ground sloths, camels, horses and several species of bison.

Humans were the triggering mechanism for the extinction. After that, predators increasingly desperate for food may have driven their prey to extinction over long periods of time and then eventually died out themselves.

"We think the evidence shows that major ecosystem disruptions, resulting in these domino effects, can be caused either by subtracting or adding a major predator. In the case of the woolly mammoths and sabertooth tiger, the problems may have begun by adding a predator, in this case humans," said Ripple.

The study has been published in the cover article of the journal BioScience. (ANI)