If there is double population of prey then it is not necessary that there will be double predator. There is a systematic pattern that is being following in certain ecosystems. A research has been carried out to know the reasons behind why there are not many lions irrespective of the fact that there are so many preys available for them.

Ian Hatton from McGill University conducted the study in which he looked at the predator/ prey ratio in parks in East and Southern Africa. He found that lions were in less number. The researchers came to know that having double population of prey does not mean double population of predator. In fact, the rule is more an ecosystem is filled with prey, less with the number of the predators.

Ian said that he has observed many ecosystems and found the same pattern. The researchers said that in comparison to the population of carnivores such as lions, leopards and hyena, population of zebra, buffalos and gazelles were in abundance.

Hatton explained, "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 researchers said that the pattern is not only applicable for carnivores, but also in herbivores and plants too. In crowded ecosystems, prey reproduces less when compared with relatively small settings.