Brain size has long been a source of fascination in the animal kingdom, often sparking debates about intelligence, evolution, and behavior. While humans pride themselves on brainpower, many animals boast brains far larger (at least in physical size). So what animal has the biggest brain? And does that mean it's the smartest? Let’s dive into the answer and explore what that massive brain actually means.
WHAT ANIMAL HAS THE LARGEST BRAIN? THE WINNER IS…
The title of what animal has the largest brain belongs to one massive marine mammal: the sperm whale.
These deep-diving giants can have a brain weighing up to 9 kilograms (20 pounds), which is the heaviest of any species on Earth. For comparison, the average human brain weighs just 1.4 kilograms (3 pounds). The sperm whale’s oversized, square-shaped head holds this incredible organ, which takes up about a third of its total body length.
The brain plays a role in sensory navigation, especially in echolocation, and helps the whale process the complex acoustics of its deep-sea world. Despite having the largest brain in an animal ever recorded, brain size alone doesn’t automatically mean greater intelligence.
WHO HAS THE LARGEST BRAIN RELATIVE TO BODY SIZE?
If we switch lenses and ask which animal has the largest brain relative to its body size, the answer isn’t a whale at all. The humble ant is the animal with the largest brain.
According to Haller’s Rule, smaller animals tend to have larger brains proportionate to their bodies. In fact, some ants have brains that make up 12% of their body weight. Humans, by contrast, sit at around 2%.
So while we may not crown ants as the smartest species, their efficient brain-to-body ratio helps them perform sophisticated colony behavior and problem-solving.
This contrast reminds us that while we often ask what animal has the biggest brain, size isn’t the only (or best) metric.
LAND VS SEA: BIG BRAINS ACROSS HABITATS
Now that we’ve answered what animal has the largest brain, let’s zoom out. Who holds the title on land?
That would be the elephant, with a brain weighing roughly 5 kilograms (11 pounds). Elephants are known for their emotional intelligence, long-term memory, and empathy. They grieve their dead, recognize themselves in mirrors, and pass knowledge across generations.
Yet, in the ocean, the sperm whale still reigns supreme. Among the biggest animals in the ocean, these whales are not just heavyweights in body mass, but in grey matter, too.
IS A BIGGER BRAIN A SMARTER BRAIN?
Not always. While it’s tempting to assume the biggest brain equals the highest IQ, the truth is more nuanced. Scientists consider the encephalization quotient, a ratio comparing brain size to body size, as a more accurate measure of intelligence.
For instance, humans and dolphins have high EQs despite smaller absolute brain sizes. Sperm whales, though massive-brained, have a relatively low EQ due to their colossal body size.
Still, these whales display signs of learning and adaptability. Historical records from the early days of whaling reveal that once sperm whales began being hunted, the success rate of harpooners dropped by nearly 60%.
That suggests these animals either learned to avoid danger or shared knowledge within their social groups to showcase a form of communication and problem-solving.
This is where studies on the intelligence of dolphins further support that brain structure, social dynamics, and learning ability matter just as much as size.
BRAIN STRUCTURE: WHAT MAKES BRAINS DIFFERENT?
Brain structure matters just as much as its size. Take the cerebellum, for example. It controls balance, movement, and some aspects of memory.
In sperm whales, the cerebellum accounts for only about 7% of total brain mass. In killer whales, it’s closer to 14%.
In humans, it lands around 10%. This means some species may allocate more of their brain toward motor skills, while others emphasize social bonding or sensory navigation.
So even when we look at the animal with the biggest brain, the functions that brain performs (and how it’s wired) tells us far more about how that animal lives and interacts with its environment.
WHO ARE THE SMARTEST ANIMALS?
If we’re ranking species by smarts and not brain weight, a few names rise to the top. Great apes like chimpanzees and orangutans are known for using tools and displaying empathy.
Elephants, meanwhile, are social geniuses. Crows and ravens, surprisingly, perform just as well as some primates in problem-solving tasks.
When comparing cognition, smart doesn’t always scale with size and the animal with the biggest brain might not crack the top five. If you're curious about the brainiacs of the animal world, check out our article on the smartest animals in the world.
FINAL THOUGHTS: BIG BRAINS, BIGGER HEARTS
As we’ve explored the question (what animal has the biggest brain?) it’s clear that size is just one part of the equation. From the colossal cerebrums of whales to the precise efficiency of insect brains, the diversity of brain design is a wonder of evolution.
Understanding how different species think, communicate, and interact with their environments gives us a deeper appreciation for their role in the world.
Here at Fahlo, we partner with non-profit organizations to create bracelets and plushes that come with a real animal to track. We started this mission in 2018, and since then, we’ve been fortunate to donate millions to help save wildlife.
By combining a tangible bracelet with an interactive tracking experience, our goal is to educate our customers and inspire a love for conservation.
If you're as fascinated by the animal kingdom as we are, join our journey. Follow the story of a whale, sea turtle, lion, and lots more species to connect to wildlife in a way that’s personal, meaningful, and fun.