Lack of lions, other predators explained by simple mathematics

An ecosystem filled with healthy and active adult makes it hard for predators to find their meal.

“If you double the prey, you should double the predators”, Hatton noted. Studies that claim that there are mathematical laws that don’t allow more lions to exist usually put the blame on growth and metabolism.

Since the 1940s, when lions count was an estimated 450,000, lion populations have declined out across the world. More prey did mean a few more lions, but the lions did not increase proportionally to the gazelle population, for example.

A better understanding of predator-prey dynamics would help conservationists monitor endangered species and could show how many large predators should be in a given area based on the available prey.

Scientists said this week they have uncovered what seems to be an unusual law of nature that keeps big predator numbers low across vast spaces of the Earth and its oceans. According to their study, the researchers also found that growth patterns throughout whole ecosystems, where prey seemed to naturally reproduce less, were found to have similar individual growth patterns. But when researcher Ian Hatton from the McGill University led his team to a closer study on this matter, he discovered something that might sound like a stupid joke to someone who hears for the first time.

The latest study is published Science journal. When there is more prey to be consumed, more predators should also be available to consume them.

The lead writer of the research, Hatton, stated that he needed to watch African animal communities with a objective to draw a comparability in between how the variety of carnivores was… However, as he looked at their figures, he discovered that the ratio of predators to their prey was “greatly reduced” in the lushest ecosystems all over the world, and that the increased crowding resulted in a reduced rate of reproduction amongst prey species, which in turn limited the abundance of their predators.

When they examined studies on other animals, the researchers saw the same pattern.

Once they observed this pattern in one setting, the researchers then began analyzing data about food pyramids, and the relationship between predators and prey in ecosystems as varied as the Indian Ocean, the Canadian Arctic and the tropical rainforests. “In fact, the prey’s rates for reproduction are limited, which limits the abundance of predators”.

When Hatton and his colleagues then started putting it all together and crunching the numbers, summing up all the carnivores and herbivores, they found a very unexpected and regular pattern.

“The discovery of ecosystem-level scaling laws is particularly exciting”, adds co-author Michel Loreau, adjunct professor in McGill’s Biology Dept. and now at the Centre national de recherché scientifique (CNRS) in France.