Wild Cat Brains Challenge Evolutionary Norms

A new study by a Michigan State University neuroscientist has revealed that the brains of wild cats don't necessarily react the same way to evolutionary pressures as those of their fellow mammals like humans and primates.

"Studying feline brain evolution has been a bit like herding cats," said Sharleen T. Sakai, a Michigan State University professor of psychology and neuroscience. "Our findings suggest the factors that drive brain evolution in wild cats are likely to differ from selection pressures identified in primate brain evolution."

Establishing and maintaining social relationships are more demanding than living alone, resulting in bigger brains. A larger frontal cortex in humans and primates is the evolutionary effect of sociality. What caught Sakai's interest was the difference when it came to wild cats' brain structure. Cheetahs are also social creatures, yet their frontal lobes are relatively small. Leopards are generally observed to be solitary beasts but have large frontal lobes.

"We wanted to know if this idea, called the 'social brain' hypothesis, applied to other social mammals, especially carnivores and, in particular, wild cats," Sakai said.

Sakai and her team examined 75 wild feline skulls from 13 species and used computed tomography (CT) scans and sophisticated software to digitally "fill in" the areas where the brains would have been to determine brain volume. Of the 13 wild feline species examined, 11 are solitary, while two lions and cheetahs are social.

Since female lions work together to defend and feed their young, hunt large prey, and protect their territory, they have a larger frontal cortex compared with male lions who sometimes live alone and are only dominant in a pride for a few years.

Previously thought to be solitary, the social cheetah, surprisingly, had the smallest brain and frontal cortex of all wild cats examined. Having a smaller brain requires less energy, possibly contributing to the cheetah's astonishing speed. "Cheetah brain anatomy is distinctive and differs from other wild cats," Sakai said. "The size and shape of its brain may be a consequence of its unusual skull shape, an adaptation for high-speed pursuits."

Another surprise is the leopard's relatively large frontal lobe. Though a solitary wild cat, the leopard is known for its flexibility and adaptability. These behaviors could also be correlated to enhanced brain processing and a larger brain size in other species.