The mysteries of animal intelligence are sometimes surprising. Killer whales use amazing hunting methods, cats can solve complex problems, and some fish can count. Animals on our planet often show abilities that can surprise anyone. So, which species has the largest brain and is there a relationship between brain size and intelligence level?

The sperm whale (Physeter macrocephalus) has the largest brain of all animals; Its weight reaches about 9 kilograms. Big brains aren’t always an indicator of high intelligence, but a 2021 study found that hunting efficiency dropped by 60 percent in the early days of industrial whaling; This may indicate that the whales have learned to avoid predation or are passing important information to each other.

The ratio of brain to body size should also be taken into account. A 2009 study found that in some ant species, the brain makes up 12 percent of the total body weight. This confirms Haller’s rule, which states that small animals generally have a higher brain-to-body ratio.

It is also useful to consider the anatomical structure of the brain. The cerebellum, which is responsible for the coordination of movements and memory, constitutes approximately 7 percent of the total brain mass in sperm whales, while this share is approximately 14 percent in killer whales. By comparison, in humans the cerebellum takes up about 10 percent of the brain mass.

According to data from a study of 1,400 mammal species, the ratio of brain size to body size varies significantly between species. For example, California sea lions have small brains relative to their body weight, while humans and dolphins have large brains and small body sizes.

There is also an interesting phenomenon of domestication syndrome, in which there is a reduction in brain size in domesticated animals compared to their wild relatives. Studies show that the brains of domesticated cow species are nearly as large as those of extinct species, but the brains of cows in constant contact with humans are smaller.

Among land animals, elephants have the largest brains and exhibit high levels of social and emotional intelligence. As for birds, some crow species display cognitive abilities on par with chimpanzees, although their brain size is much smaller. Kan Kabadayi from Lund University comments, “Brain size alone is not a determining factor on intelligence.”

There is a wide range of brain sizes across the animal kingdom, and many studies have been done to examine how this affects intelligence. Brain potential can be distributed among different functions, such as visual processing, social interactions, or complex cognitive tasks. However, among all species, sperm whales stand out for their large amount of gray matter, indicating significant brain potential. Source