Today I’m going to talk to you about dolphin intelligence and in particular their use of tools, methods of communication, sonar and also their sensory capacity.
But first let’s look at how the dolphin brain compares to the brains of other species in terms of size. The largest brain in the world belongs to the sperm whale. Weighing some 9,000 grams, it is six to seven times larger than the human brain. The second largest brain in the world is the killer whale (or orca) at 6,000 grams. The next largest brain among the marine mammals is the bottlenosed dolphin at 1,500 grams, followed by human brains at approximately 1,200 grams. Strong connections between the sensorial and motive areas of a dolphin’s brain to the body indicate that it is very much sensitive to pain and stress.
Looking at the way dolphin’s use tools, while many believe that primates, such as chimpanzees, are the only species who use tools for activities, dolphins studied in the wild have been seen using sea sponges to protect their snouts from getting scratches as they scavenge for food on the ocean floor. Dependent calves, young baby dophins, are also provided with sponges from their mothers, as research in the wild has seen infant dolphins wearing tiny sponges on their snouts while swimming close to their mothers.
With regards to dolphin communication, dolphins utilize “signature whistles” to identify themselves to others. In other words, these whistles can be seen as representing their names. Furthermore, dolphins also mimic movements, of both humans and other animals.
Another interesting point about dolphins is of course their sonar. It has been suggested by several noted scientists that dolphins may be able to create acoustical holographic images from the interlacing of their sonic output. It is well known that dolphins can see inside the bodies of their fellow dolphins, and other animals in the water. This is because dolphin sonar evolved to pass through water and does not reflect until it hits something like bone or air sacs. Since animal bodies are more than 50% water, their sonar enables them to literally “see” inside other animals.
And finally, dolphins have fantastic sensory capacity. They have the ability to focus their eyesight due to the curvy characteristics of their lenses, thus they are able to see both in and out of water. Moreover, dolphins have little more than a small hole for hearing, as having larger ears would severely affect the creature’s ability to swim. Rather, studies show that sounds are obtained through tiny bones, and then are transferred to the inner ear through the fatty material that surrounds the eardrum. Adapted from here.

1. sensory capacity
2. 1500 grams / 1500g
3. primates / chimpanzees
4. movements
5. yes
6. a small hole / small hole

• capacity = ability
• indicate = show / point to
• primate = monkey
• snouts = noses (for dolphins and pigs)
• scavenge = hunt / forage
• infant = new born / child
• mimic = copy