Biologists plot ancient ecosystem with massive super predators
Oct 28 2015
The paper notes that many of today's endangered species evolved during or before the Pleistocene epoch, and under very different conditions from today's.
Using teeth fossils of Pleistocene predators, the researchers were able to develop size estimates of the animals. Moreover, when they gathered in packs the animals would have terminated a 9-year-old mastodon that weighed up to 2 tons.
Leading the other researchers, a UCLA evolutionary biologist, Blaire Van Valkenburgh, that the lions of this age were much larger than those of today, and so were able to attack and kill a number of giant ground sloths and mastodons among others; and this prevented the large herbivores from overrunning the Pleistocene ecosystem which ended almost 11,700 years ago.
More work is expected to remake Pleistocene environments, "which were in obvious immensely not quite the same as today", Van Valkenburgh said. The team found that hypercarnivores such as cave hyenas and saber-toothed cats preyed on megaherbivores that led to the latter's declining numbers. Van Valkenburgh said that larger pack sizes, which may have been more common in the Pleistocene, further enhance hunting success.
Despite today's megaherbivores including elephants being largely immune to natural predators, herbivores in ancient times met their match in hyper-carnivores. In true, they had always been asking themselves how did the ecosystem run with so many herbivores in charge, that could have easily destroyed the environment, but it seems the herbivores were not the bosses after all.
Previous research then helped the scientists develop estimates of an animal's size based on just its first molar.
The curved and serrated dagger-like canines of a sabre-toothed cat, or Smilodon, were seven inches long and one bite to the neck could instantly sever crucial arteries of a mammoth or mastodon.
"The difficulty is that, even with the best measurements, modern adult elephants with the same shoulder height may vary by as much as two times in body mass".
By looking at the sizes of modern carnivores and the preferred sizes of their victims, the scientists then estimated what sizes of prey ancient predators might have targeted.
They conclude juvenile mastodons and mammoths would indeed have been susceptible - especially if the carnivores were socially organised.
Indirect evidence that ancient predators hunted in larger groups than they do today may come from fossil teeth. Among advanced carnivores, when rivalry over prey is high, prey is harder to catch, and carnivores make the most out of corpses by eating more bone, prompting higher rates of broken teeth.
Because there is no way to infer from the scant fossil evidence whether the carnivores hunted in packs, the scientists relied on estimated prey sizes and modeled the capacity of single predators and predators in groups to take them down. New research suggests predatory animals protected local plant life by keeping the large vegetarians in check. "By understanding what we lost, what the efficiency of the planet was, we can take in more about the time in which our species developed and possibly why we've thus done well".