Scientists discover why Serengeti animals stick together

November 14th, 2007 - 2:56 am ICT by admin  
Lead author John Fryxell, an integrative biologist at the University of Guelph in Canada, said group behaviour ensured greater stability in number, for the species concerned.

While for animals like wildebeest, herding implied security from predators, for apex predators like lions, a pride ensured territorial defence and protection of their cubs, she said.

“The greater the tendency to form groups, the higher the stability of numbers of both species over time,” said Fryxell.

For their study, Fryxell and University of Minnesota ecologist Craig Packer examined a slew of data on predatory lions and their prey - plant-eating wildebeest - living along Africa’s Serengeti Plains.

They also studied four decades of reported observations on lion behaviour and population numbers, data on lion-hunting behaviour and success, and censuses of wildebeest and other herbivore herds in the area.

Findings revealed that when the wildebeest aggregated in clumps, the lions were less likely to hunt them, resulting in a lower consumption rate for each lion than when the wildebeest lived as individuals.

When both the lions and wildebeest formed groups, prey intake plunged even more.

Compared with no-group ecosystems (all animals strewn across the Serengeti), grouping caused a 90-percent reduction in kill rates for lions, they study revealed.

With the data, the scientists also used computer models to figure out how group-living by just prey or predator, as well as by both species, affected their respective populations and the ecosystem as a whole.

They found that the reduction was similar to what had been found for another predator-evading strategy - seasonal migration.

Several prey species, including wildebeest and zebra, spent most of the year in areas far out of reach of a given lion pride. If practiced in tandem, with herds of wildebeest migrating, they could reduce being eaten by two orders of magnitude, the findings revealed.

The study further revealed that though lions in prides often got less food compared to the ones that led a solitary existence, overall, the social cliques worked as ecosystem stabilizers, with both lion and wildebeest populations remaining relatively level over time.

In contrast, when both species wandered the plains singly, the models showed the numbers of individuals in both populations were erratic and unstable; cycling from highs to lows and likely leading to the extinction of both predator and prey, reports LiveScience. (ANI)

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