Double population of prey does not mean double predator. A systematic pattern is observed in various ecosystems, which had not been noticed previously.
Why are there not more lions, despite the fact a lot of prey is available for them?
To find the answer, Ian Hatton, a PhD student at McGill University looked at the predator/ prey ratio in dozens of parks in East and Southern Africa and came up with surprising calculations. Lions were less in numbers than anticipated.
Researchers found that double population of prey does not mean double population of predator, as it is generally expected. Instead, the more an ecosystem is crowded with prey; the less will be the predators.
Hatton led team looked at many ecosystems and discovered same pattern there as well. They found carnivores such as lions, leopards and hyena have an abundance of zebra, buffalos and gazelles in the parks but the population of predators was low in proportion to the prey.
“Until now, the assumption has been that when there is a lot more prey, you’d expect more predators,” said Hatton. “But as we looked at the numbers, we discovered instead, that in the lushest ecosystems, no matter where they are in the world, the ratio of predators to their prey is greatly reduced. This is because with greater crowding, prey species have fewer offspring for every individual. In fact, the prey’s rates for reproduction are limited, which limits the abundance of predators.”
The pattern was not limited to just carnivores, it was observed in herbivores and plants too. Researchers discovered that in every ecosystem it happens in a very systematic way. In crowded ecosystems prey reproduce less than in the relatively small settings.
The findings are surprising and suggest a level of organizational structure and function in ecosystem that has not been noticed before. Many researchers are already calling it the discovery of a new law of nature.
“We kept being astonished,” said Kevin McCann, the co-author and professor of Integrated Biology at Guelph University. “This is just an amazing pattern.”
Don't Miss: See the first leaked Black Friday 2016 Ad
In dense, crowded environments, animals breed more slowly, meaning their population will be mostly made up of healthy adults. It is easier for a predator to target a young or old prey since they are weak than a healthy adult. An environment filled with healthy and adult animals makes it difficult for predators to find their meal. Therefore, the number of prey animals increased, but predators declined in a very predictable way.