Packs of immense lions and other predators long ago helped keep populations of huge plant-eaters such as mammoths from overrunning ecosystems, according to new research.
Scientists have long wondered how ecosystems during the long Pleistocene epoch, which ended around 12,000 years ago, survived despite the presence of many huge, hungry herbivores, such as mammoths, mastodons and giant ground sloths.
Observations of modern elephants suggest that large groups of those animals could have basically destroyed the environment, but they didn’t.
The findings, reported this week in the journal Proceedings of the National Academy of Sciences, suggest that intense, violent attacks by packs of some of the world’s largest carnivores—including lions much bigger than those of today and sabertooth cats—did more than make their victims’ lives miserable. They also went a long way toward shaping ecosystems.
The research could have implications for conservation efforts today, the researchers argue. They note that many of today’s endangered species evolved during or before the Pleistocene, and under very different conditions from today’s. “Recreating these [Pleistocene] communities is not possible, but their record of success compels us to maintain the diversity we have and rebuild it where feasible,” the researchers write.
Led by Blaire Van Valkenburgh, an evolutionary biologist at the University of California Los Angeles, they found that thanks to their larger size, the ancient carnivores were more than able to kill young mammoths, mastodons and other species.
The largest of the “hyper-carnivores” such as lions, sabertooth cats and hyenas died out during the late Pleistocene, they added, probably because of the disappearance of their preferred prey, including young “mega-herbivores”—mammoths, mastodons and giant ground sloths.
“Based on observations of living mega-herbivores, such as elephants, rhinos, giraffes and hippos, scientists have generally thought that these species were largely immune to predation,” because they’re big and ably protect their young, said Van Valkenburgh.
But “data on modern lion kills of elephants indicates that larger prides are more successful,” she went on. “We argue that Pleistocene carnivore species probably formed larger prides and packs than are typically observed today—making it easier for them to attack and kill fairly large juveniles and young adult mega-herbivores.”
The scientists used several different methods to estimate information about the Pleistocene animals.
One method was to examine tooth fossils and apply the ratio of tooth size to body mass of today’s animals. This led the researchers to estimate that the extinct species were between 50 and 100 percent larger than today’s tigers, African lions and spotted hyenas. Another method was to analyze data on 50,000 instances of kills in the wild to estimate the typical and maximum sizes of the Pleistocene prey.
Today’s large predators benefit their ecosystems in part by providing carcasses that feed an array of smaller species. The same was true during the Pleistocene, the researchers argue: keeping mega-herbivores in check left more vegetation for smaller mammals and birds to eat. River areas might also have benefited, since more plants would protect river banks from erosion.