Aug. 18, 2006 — Predators prefer to chase smaller-brained prey, which often lack the mental fortitude to escape their brainier hunters, according to a recent study.
The findings, published in the Royal Society Journal Biology Letters, suggest brain size evolution may be driven by predator-prey relationships since, like a perpetual "Road Runner" cartoon, each side is forever trying to outwit the other.
While there has been a consistent increase in relative brain size, and therefore intelligence, over most mammal groups throughout evolutionary time, predator-prey relationships have led to an intelligence divide, said lead researcher Susanne Shultz.
"One could make the argument that there has been an arms race of sorts between prey and their predators, said Shultz, a scientist in the Evolutionary Psychology and Behavioral Ecology Research Group at the University of Liverpool, England. "As prey get better at evading their predators, there is strong selection on predators to adopt counter strategies to better catch prey."
Shultz and colleague R.I.M. Dunbar studied data on animals from five forest communities in two continents. The animals came from Taï National Park in West Africa, the Ituri forest in the Republic of Congo, Mahale National Park in Tanzania, Kibale National Park in Uganda and Manu National Park in Peru.
The predators, which included leopards, chimpanzees, jaguars, pumas and other animals, were found to most often go for tinier brained prey, such as the small antelope, mongooses and the red river hog.
When the scientists ran all of the data through several statistical tests, they determined relative brain size was the most important predictor of biases in predator diets. Body size and prey group size were two other contributing factors, but nothing trumped brain size in predicting what a predator would choose for its dinner.
