Cetacean intelligence

Cetacean intelligence is the ability to think and solve problems shown by aquatic mammals called cetaceans. This group includes baleen whales, porpoises, and dolphins. These animals live in the water and have surprised scientists with their smart behaviors.

In 2014, a study discovered that the long-finned pilot whale has more special brain cells, called neocortical neurons, than any other mammal studied so far, including humans. This shows just how clever these ocean animals can be. Scientists continue to learn more about their amazing minds and how they use them to live in the sea.

Brain

Size

Brain size used to be thought of as a big clue to how smart an animal is. But now we know there are many other things that affect intelligence too, like how the brain works. Scientists have learned a lot from studying how smart birds are, and this makes them think that brain size might not be the only thing that matters.

When we look at how big an animal's brain is compared to its body, we can get a better idea of how smart it might be. This is called the brain to body mass ratio. Some dolphins, porpoises, and whales have a higher ratio than humans, meaning their brains are bigger compared to their body size than ours are.

• Sperm whales have the biggest brains of any living animal, weighing about 7.8 kg in full-grown males.
• Orcas come next with brains weighing between 5.4 and 6.8 kg.
• Bottlenose dolphins have brains that weigh between 1,500 and 1,700 grams. This is a bit more than human brains (1,300–1,400 grams) and about four times bigger than chimpanzees (400 grams).

Structure

In 2014, scientists found that a type of dolphin called the long-finned pilot whale has more cells in a special part of the brain than any other animal studied so far, including humans. Dolphin brains are different from land animals because they have a special area that might help them process sounds and feelings.

Because dolphins need to breathe on their own, even when sleeping, they seem to rest one side of their brain at a time. This might help them stay alert for danger. Dolphins also rely more on sound than sight, so the part of their brain that handles sound is much bigger than the part that handles sight.

Brain evolution

The brains of cetaceans, such as whales and dolphins, have evolved in ways similar to those of primates. Over time, their brain size, body size, and brain complexity have generally increased. However, some groups of cetaceans actually lost some brain complexity, though scientists are still unsure why this happened.

Research suggests that the growth in brain size and complexity in cetaceans may have been driven by the need to manage complex social groups. Other factors, such as changes in what they eat, the development of echolocation, or needing to cover larger areas, might also have played a role.

Problem-solving ability

Some studies show that dolphins can understand ideas like numbers, even if they can't count exactly. They can tell different numbers apart.

Researchers who study how animals learn to recognize groups often say that dolphins are about as smart as elephants. Dolphins are very good at learning, but they are not smarter than some other clever animals.

Behavior

See also: Whale § Life history and behavior

Dolphin groups can vary a lot in size. River dolphins usually stay in small groups of about six to twelve, and they know each other well. Some dolphins, like the pantropical spotted dolphin, common dolphin, and spinner dolphin, travel in much larger groups of hundreds. These big groups can move together as one when they sense danger, showing they are aware of each other.

Orcas in British Columbia, Canada, and Washington, United States, live in family groups led by an older female. These groups stay together for a long time and have their own special sounds to communicate. Bottlenose dolphins also form strong groups, with females connecting directly or through friends, and males forming teams to help each other.

Dolphins love to play, making bubbles and rings underwater and enjoying the shapes they create. They have also helped humans in need and can learn new tricks. Some dolphins have even used tools, like wrapping sea sponges around their noses to protect themselves while searching for food on the ocean floor.

Communication

Further information: Whale vocalization and Human–animal communication

Whales and dolphins use many kinds of sounds to talk to each other and sense their surroundings. Toothed whales, like dolphins, make three main types of sounds: clicks, whistles, and pulsed calls.

• Clicks are quick sounds made in rapid series to find out about objects around them using echoes.
• Whistles are used to talk to each other, like a special call that acts like a name for each dolphin.
• Pulsed calls are used by some whales, like orcas, and have special tones and patterns.

Dolphins can even learn human sign language and understand simple sentences. They remember each other's whistles even after many years apart, showing they have very good memories.

Self-awareness

Self-awareness is an important ability that helps animals think about their own actions, similar to how humans do. Scientists believe that bottlenose dolphins, along with elephants and great apes, may have this ability.

One way scientists test for self-awareness is by using a mirror. They put a mark on an animal and see if it recognizes itself in the mirror. Dolphins have been shown pictures of themselves on television and seemed to understand it was them, which suggests they might be self-aware. However, some scientists think more tests are needed to be sure.