Being clever, it seems, is a good way to avoid being eaten. Predators such as chimpanzees and wild cats tend to hunt small-brained prey that are less able to think their way out of a tight corner.

Robin Dunbar and Susanne Shultz of the University of Liverpool, UK, examined predator and prey relationships in five forest communities, and found that the most important factor determining which prey chimps and cats like to eat was the relative size of its brain (Biology Letters, DOI: 10.1098/rsbl.2006.0519).

The explanation, say Dunbar and Shultz, is that while prey species implement a wide variety …