Smaller animals have larger brains relative to their bodies.
If terms like"bird brain" and"harebrained" are any indication, animal brains present fascinating and diverse examples of one of the most complex organs known to science. Animal brains differ not only in overall size but also in their size relative to the animal's body mass.
A 2009 study in the journal Brain, Behavior and Evolution found that an especially tiny genus of ant has the largest brain for its body size. Brachymyrmex has an average body mass of up to 0.049 milligrams and an average brain mass of 0.006 milligram. That means its brain is roughly 12% of its body mass, giving it a brain-to-body-mass ratio of about 1:8.Why do animals evolve larger brains?In absolute terms, animals' brain size tends to increase with the size of the animal.
But, brain size isn't a perfect predictor of animal intelligence. The brain of an African elephant weighs 10 pounds , on average, according to a 2014 study in the journal Frontiers in Neuroanatomy , three times larger than the human brain. Their large brain size is due in part to their massive cerebellum, used to coordinate the muscle activity in their trunk and ears, according to Scott.
"If you look at the brain of a rabbit, a cat and a small monkey, they're not that different in size, but their behavior is going to be very different because of the nature of the brain cells," Scott said."By the time you get to the monkey, you're seeing a primate brain, with proportionally larger frontal lobe areas and more curiosity-driven behavior."