Dolphins possess a single brain, much like humans do. Despite their sophisticated capabilities, these marine mammals operate with one highly developed brain.
Unpacking the Single Dolphin Brain
Like all mammals, dolphins have a brain divided into two distinct hemispheres. These hemispheres coordinate the dolphin’s functions and behaviors. A unique adaptation is unihemispheric slow-wave sleep, where one half of the brain sleeps while the other remains awake and alert.
This specialized sleep pattern allows dolphins to surface for air, as their breathing is a conscious process. The active hemisphere helps them remain aware of their environment. Dolphins alternate sleeping hemispheres, ensuring both halves receive adequate rest.
Inside the Dolphin Brain: Structure and Size
The dolphin brain is large. A bottlenose dolphin’s brain typically weighs around 1.6 to 1.7 kilograms, which is slightly heavier than the average human brain, usually weighing between 1.3 and 1.5 kilograms. When considering brain size relative to body weight, dolphins have a ratio close to humans.
The dolphin brain features a highly folded cerebral cortex with many gyri (ridges) and sulci (grooves). This extensive folding increases the surface area of the cortex, which is involved in higher cognitive functions. While dolphin brains have a large cortical surface area, their neocortex can be relatively thin compared to that of terrestrial mammals. Neuron counts vary among dolphin species; for instance, bottlenose dolphins have approximately 5.8 billion neocortical neurons, while some species like the long-finned pilot whale have been found to possess around 37.2 billion neocortical neurons, which is more than humans.
Beyond Size: Cognitive Capabilities
The complex structure of the dolphin brain underlies their impressive array of cognitive abilities. Dolphins exhibit sophisticated communication systems, including a variety of whistles and clicks, and use unique signature whistles to identify each other. Their problem-solving skills are well-documented, allowing them to navigate challenges and learn complex tasks. Dolphins also display advanced social intelligence, forming complex social groups and alliances within their pods. They show self-awareness, demonstrated by their ability to recognize themselves in mirrors, a trait rare in the animal kingdom. Specialized brain cells called spindle neurons, also found in humans and great apes, suggest a capacity for complex emotional processing and social cognition.