Lions are not really disappearing, but the predators have a smaller population compared to their prey. While most people would think that more prey would in turn cause more predators, it's actually the other way around.

A team of scientists had been wondering why there aren't more lions, and found that a simple mathematical equation function which they call the "power scaling law."

The patterns that link prey and predator species, specifically of lions and their catch, were discovered among diverse ecosystems by ecologists from the University of Guelph, including researchers from the McGill University, the University of British Columbia and the Perimeter Institute for Theoretical Physics in Waterloo, Ontario. Findings were published on Sept. 4 in the online journal Science.

According to integrative biology professor Kevin McCann from the University of Guelph and co-author of the paper, they found the amounts of predator and prey biomass to be "remarkably well-predicted by a simple mathematical function."

The "power scaling law" revealed that in diverse ecosystems, there will always be fewer predators than expected, compared with those in resource-poor environments. From grasslands to forests to lakes and oceans, biomass production measurements were analyzed. In their study, the researchers looked at over 1,000 previous studies in the last 50 years which were conducted in over 1,5000 locations across the world.

"We kept being astonished," McCann said, remarking on the amazing pattern among diverse ecosystems. The same predator and prey ratios were found in whichever location they analyzed. The more there were preys in an ecosystem, the less there were predators.

Co-author John Fryxell, who is also an integrative biology professor at the University of Guelph said that in resource-rich ecosystems, you might expect predator biomass to increase as well, but the ration of predators to prey says otherwise.

The researchers also looked at data on food pyramids, along with the predator-prey relationships in ecosystems in varied areas like the Canadian Arctic, the Indian Ocean and the tropical rainforests. The researchers also found the predator and prey relationship to be similar the patterns of individual growth. Jonathan Davies from the Department of Biology at McGill University, mentioned how the speed of growth declines as size increases. "The cells in an elephant grow more than 100 times more slowly than those in a mouse," explained Davies, who also co-authored the study.

Photo: Derek Keats | Flickr