New law of nature: Here's why there aren't more lions

It seems like a recent study has discovered a new law of nature, in which more crowding leads to fewer offspring.

Why aren't there more lions? That is what puzzled a McGill student Ian Hatton, when he started looking at the proportion of predators to prey across dozens of parks in East and Southern Africa.

In this case, the answer had nothing to do with isolated human hunters. The parks were teeming with potentially tasty treats for the lions. So, one might imagine that the population of lions in each park would increase to match the available prey.

Instead, what Hatton and the McGill-led team discovered was that, in a very systematic way, in crowded settings, prey reproduced less than they did in settings where their numbers were smaller. Moreover, they found this same pattern in a whole range of different ecosystems.

It's a surprising finding that suggests a level of organizational structure and function in ecosystems that had not previously been recognized. Although biologists have long known of very regular mathematical laws governing functions in the body like metabolism and growth, no study has ever shown that similar kinds of laws may exist at a whole other level: that of ecosystems globally. Some scientists are already suggesting that it may well be the discovery of a new law of nature.

What the researchers also found intriguing was that the growth patterns they saw across whole ecosystems, where large numbers of prey seemed naturally to reproduce less, were very similar to the patterns of growth in individuals.

Co-author Michel Loreau said that the discovery of ecosystem-level scaling laws is particularly exciting, adding that their most intriguing aspect is that they recur across levels of organization, from individuals to ecosystems, and yet ecosystem-level scaling laws cannot be explained by their individual-level counterparts.

The study appears in the journal Science.