![]() Several prey species, including wildebeest and zebra, spend most of the year in areas far out of reach of a given lion pride. The reduction was similar to what the researchers found for another predator-evading strategy-seasonal migration. Compared with no-group ecosystems (all animals strewn across the Serengeti), grouping caused a 90-percent reduction in kill rates for lions. When both the lions and wildebeest formed groups, prey intake plunged even more. The ecologists found that when wildebeest prey aggregated in clumps, the lions were less likely to snag them, resulting in a lower consumption rate for each lion than when the wildebeest lived as individuals. ![]() With the data, they used computer models to figure out how group-living by just the prey or predator, as well as by both species, would affect their respective populations and the ecosystem as a whole. "And group-living reduces predators' efficiency to the point where co-existence is likely to be the rule rather than the exception."įryxell, Packer and their colleagues examined a slew of data on predatory lions and their prey-plant-eating wildebeest-living along Africa's Serengeti Plains, including: four decades of reported observations on lion behavior and population numbers, data on lion-hunting behavior and success, and censuses of wildebeest and other herbivore herds in the area. "Most highly vulnerable prey species form herds, swarms, schools or flocks," Packer said. "Traditional ecological models have erroneously predicted that predators would inevitably over-exploit their prey, leading to frequent population crashes," said Fryxell's co-author, University of Minnesota ecologist Craig Packer. (The study scientists defined a social group as occurring when animals live within an area of two hectares, or about five acres, of one another.) That's because the playing field changes when the animals form groups such as lion prides or herds of wildebeest. In reality, observers see fewer population booms and crashes. ![]() For instance, an ecologist could say that as the numbers of plant-eating wildebeest soar so will those of their lion predators, with booms and crashes normally following. 25 issue of the journal Nature.Įcological theory generally describes how animal populations interact based on their individual numbers.
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