What Animal Has the Largest Brain-to-Body Ratio?

When we think about brain size, we often assume that bigger animals must have bigger brains. While this is true in terms of raw size, the more interesting question is about the brain-to-body ratio: how large an animal's brain is compared to its body. This ratio is often used to give a sense of how "intelligent" an animal might be, although it's not the only factor. Let’s dive into the fascinating world of animals with the largest brain-to-body ratios, starting with the creature that tops the list.

1. Tree Shrews – The Ratio King

The tiny tree shrew holds the title for the largest brain-to-body ratio of any known animal. These small mammals have a brain that is about 10% of their body weight, an impressive proportion! For comparison, humans’ brain-to-body ratio is around 2%. Tree shrews live in Southeast Asia, and despite their small size, they are incredibly agile and quick learners. While their intelligence is difficult to measure, their high brain-to-body ratio suggests they might be more capable than they appear.

2. Humans – Big Brains, Small Bodies

Coming in second place are humans. Our brains make up roughly 2% of our body weight, and while that might seem small compared to the tree shrew, our brains are significantly larger in absolute terms and packed with neurons. The human brain is highly complex and allows for advanced reasoning, problem-solving, language, and creativity, all of which make us one of the most intelligent species on the planet.

3. Dolphins – Smart Swimmers

Next up are dolphins, known for their playful behavior and high intelligence. Dolphins have a brain-to-body ratio of about 1.2%, which is quite large for an aquatic animal. Their large, complex brains help them communicate with one another, solve problems, and exhibit social behaviors similar to those seen in humans and other primates. Dolphins are also known to be self-aware and capable of learning complex tasks, further highlighting their impressive cognitive abilities.

4. Elephants – Gentle Giants with Big Brains

Although elephants are the largest land animals, their brain-to-body ratio is lower than that of smaller animals, at about 0.2%. However, elephants have the largest brains of any land animal in absolute size, weighing over 11 pounds (5 kg). Elephants are known for their incredible memory, emotional intelligence, and social bonds. They can recognize themselves in mirrors, mourn their dead, and even use tools, showing a level of intelligence that matches their enormous brains.

5. Crows and Ravens – The Brainy Birds

Among birds, crows and ravens have an impressive brain-to-body ratio, which is around 1-2%. These birds are often referred to as "feathered apes" because of their intelligence. They can use tools, solve puzzles, and even recognize human faces. Some crows have been observed dropping nuts onto roads so that cars can crack them open—showing not only intelligence but also the ability to adapt their behavior to new situations.

6. Octopuses – The Ocean’s Clever Invertebrates

Surprisingly, octopuses are often mentioned when talking about animals with high brain-to-body ratios, although their exact ratio is hard to pin down. They have large, complex brains relative to their body size and exhibit remarkable problem-solving skills. Octopuses can escape from enclosures, open jars to get food, and use camouflage to hide from predators. Their intelligence is one of the most impressive in the invertebrate world, making them an exception among animals without backbones.

7. Squirrels – Small but Smart

Another small mammal with a relatively high brain-to-body ratio is the squirrel. While not as high as tree shrews or humans, squirrels are known for their intelligence when it comes to gathering and storing food. They can remember the locations of hundreds of hidden nuts and use clever tactics to trick potential thieves. Their brain-to-body ratio is around 1%, helping them survive and thrive in both urban and wild environments.

Does a High Brain-to-Body Ratio Mean More Intelligence?

While a high brain-to-body ratio often suggests that an animal is intelligent, it’s not the only factor. The number of neurons, particularly in the brain’s cortex, is a major contributor to cognitive abilities. Humans, for example, have far more neurons than any other animal, which explains why we have such advanced thinking and problem-solving skills compared to other species.

The animal with the largest brain-to-body ratio is the tree shrew, a small but mighty mammal with a brain that’s a whopping 10% of its body weight. Humans, with our large and complex brains, follow closely behind, while dolphins, crows, and octopuses also rank high on the list. Although brain-to-body ratio is an interesting measure, it’s not the only way to gauge intelligence. Each of these animals has evolved a brain size that suits its unique environment and lifestyle, showing that intelligence comes in many forms across the animal kingdom.

animal tags： Squirrels