Dolphins hunt, survey surroundings, avoid predators, and navigate in murky or dark waters using echolocation. Echolocation consists of clicks, squeaks, creaks, buzzes, and whistles. All of these sounds, produced as air is pushed past the dorsal bursa of a dolphin’s nasal region, are characterized by high-frequency sound waves. Dolphins, other odontocetes, and many species of bats produce these sound waves and then receive and interpret the resulting echo which is formed when the sound waves come into contact with an object. The main area of sound reception is in specialized lipid structures of the jaw-bone. Characteristics of the outgoing and incoming information are integrated to give the animals an accurate representation of an object including its location, shape, density, and velocity.
Dolphins can also communicate using high-frequency sounds by a complex system of whistles and squeaks. The highest frequencies (between 40 and 150 kHz) are used mostly for processes listed above, but vocalizations ranging from .2 and 50 kHz are used in social communication and interaction. Dolphins have their own unique signature whistles (5 to 20 kHZ) with newborns acquiring their own around 1 month of age. Signature whistles can be used to identify each other and maintain group cohesion. Schools of dolphins might come to aid an injured dolphin when hearing calls and help it, keeping it at the surface so it can breathe. Many times from Vivamar’s obervation there is a single animal seen, the so called ‘scout’ that is inspecting/searching for food. Such animals are often in acoustic connection with their conspecifics, and if they find food may call other group members to join in feeding.
Animal cognition refers to how an animal understands and comes to know its environment and its relationship to its environment through thinking, learning, remembering, decision making, and producing behavior. You are probably already familiar with some of the species that exhibit a high level of cognition such as great apes, elephants, some parrots and, yours truly— dolphins.
Even though these species have evolved separately, they each exhibit tell-tale signs of intelligence. Cognition has evolved independently in different species (this is called convergent evolution) as a result of certain social and environmental pressures that require animals to adapt to problems and opportunities. There are several characteristics that these species of higher-level intelligence have in common: they all have high encephalization levels, extended periods of parental care (link to other section), and complex social structures.
The encephalization level or quotient (EQ) compares the brain mass of an individual to a predicted brain mass for the individual (a result of an average weight of the animal). The ratio offers insight into the degree of intelligence of animals.
EQ = brain−weight
The EQ of bottlenose dolphins is 5.26. A human’s EQ is about 6.56.
For perspective, a chimpanzee’s EQ is about 2.63 and an African gray parrot’s, 1.00. For a more comprehensive table, click here.
There are several ideas about how cognition evolved in animals. One of them suggests that intelligence in social animals has evolved as a result of environmental complexity (Godfrey-Smith). More specifically, the Social Intelligence and Social Brain Hypothesis suggests that higher-level cognition and enlarged forebrains evolved due to challenges associated with a complex social environment. So, in this theory, complex social structures play a large role.
As the amount of individuals and interaction in a group increases, so does the amount of information that a dolphin has to remember about its relationships. Dolphins can keep track of who their family and group members are, who’s the best playmate, each member’s status in a hierarchy, who is most or least likely to cooperate (share food or offer protection), etc. The relationships that develop can be strong and lasting, with information stored in both short and long term memory. In a truly fascinating study by Jason Bruck, Bruck showed that dolphins have multi-decade long memory for their old tank mates’ individual whistles (which are like names for humans).
Not only do dolphins learn about and remember other individuals in their group, they also learn from them. There is evidence that dolphins exhibit social learning in a form that some scientists refer to as “cultural transmission”. In the case of marine sponges, dolphins learn by “vertical social transmission” (as in mother to offspring) to use sponges as a tool for foraging. A female calf will learn from her mother to pick a sponge off of the sea floor and wear it around on her rostrum while she forages for food in nooks and crannies of rock beds to protect her sensitive rostrum from being cut or scratched while searching for food.
To learn and remember all these things puts a type of mental pressure on dolphins. It’s “pressures” like this that may have selected for cognition in dolphins. The environmental and social pressures that dolphins experience have cultivated an intelligence that isn’t restricted to the context of their natural environments. Since research on dolphin behavior began around the 1960’s, researchers have learned many exciting and fascinating new things about what dolphins are capable of. Studying dolphins in captive research settings has given us a lot of insight into what dolphins can do that makes them special. Louis Herman has spent an entire career researching what dolphins are capable of. His findings have shaped the way we see dolphins, and are very important for offering incentive to continue to care about our ambassadors of the sea and to preserve and protect them and their environments for generations to come. So what are some of the things that Herman and his gang has taught us?
Immediate memory of things seen and heard.
Dolphins can remember sounds or items that they have seen in lists of up to 6 different items. They can also plan, meaning they can remember things for future use and use tools, which requires memory of an object’s functions and usefulness.
The ability to imitate sounds and behaviors by forming analogies between the human and dolphin body.
When researchers or dolphin trainers request the dolphins to imitate a behavior through either a gesture or symbolic sound, the dolphin can mentally represent its own behaviors to copy those of the human. For example, if a trainer asks a trained dolphin to imitate them as he or she raises a leg, the dolphin will raise its tail. If the trainer waves an arm, the dolphin will wave its pectoral fins. This ability may have evolved because dolphins are known to synchronize their behaviors while feeding or interacting with other members of the group. What’s remarkable is that they are also capable of transferring this synchronization to another species: humans!
The ability to understand meaning of words and changes in word order (“semantic” and “syntactic”).
Dolphins are among few species (great apes, humans, parrots being the others) that can recognize auditory or visual symbols as words that can be strung together according to a grammatical rule to make a sentence. Even more impressively, they can understand changes in overall sentence meaning when the order of the words in a sentence changes.
A concept of representation.
When you watch TV, chances are very high that if you see a car racing across the screen, you know it’s not going to pop out of the other side of the television when it gets to the edge of screen. This means that you have a concept of representation, that the images on the screen are symbolic of real life, but are not real life itself. Dolphins have this ability as well! In an experiment conducted by Louis Herman, dolphins watching TV for the first time were all able to distinguish the image from reality. When the televised trainers asked for certain behaviors, the dolphins produced those behaviors. But when a ball was thrown on the screen, used as a symbol for “fetch the ball”, the dolphins understood that the televised ball was a representation of a real ball, and went directly to the location of the real ball to retrieve it, instead of trying to retrieve the ball on the TV screen.
You may already be aware of “mirror-tests” which are used to help determine if an animal has self-awareness. Some dot or marking is placed on an animal that can’t be seen without a reflection, and the behavior of the animal is then observed in front of a mirror. If an animal acts differently, usually by inspecting it closely for a certain amount of time or by trying to remove it, that animal is said to have some degree of self-awareness. Dolphins, a handful of primates, elephants, and some of the more clever species of birds are some of the few species that indicate this self-awareness with a mirror-test.
Stan Kuczaj and Lauren Highfill are a couple of researchers who have observed wild and captive dolphins participating in collaborative behavior that looks quite similar to what we humans would call playing. They’ve observed young dolphins taking turns pushing one another along the surface of the water at high swim speeds. Dolphins have also been seen to play keep away or passing games with floating objects such as seaweed or plastic. Surely one of the most interesting examples of play in dolphins is the way they can form bubble rings, and then manipulate their shape and speed underwater, sometimes even sending a bubble ring through a larger bubble ring! Here is a very entertaining video of them engaging in this playful behavior.
Bruck, J. Decades-long social memory in bottlenose dolphins. Proceedings of the Royal Society Biological Sciences. 7 October 2013, Vol.280(1768).
Godfrey-Smith, P. Environmental complexity, signal detection, and the evolution of cognition. M. Bekoff, C. Allen, G.M. Burghardt (Eds.), The Cognitive Animal, MIT Press, Cambridge, Mass (2002), pp. 135-141.
Herman, L.M. Exploring the cognitive world of the bottlenose dolphin. M. Bekoff, C. Allen, G.M. Burghardt (Eds.), The Cognitive Animal, MIT Press, Cambridge, Mass (2002), pp. 275–283.
Krützen, Michael ; Mann, Janet ; Heithaus, Michael R ; Connor, Richard C ; Bejder, Lars ; Sherwin, William B. Cultural transmission of tool use in bottlenose dolphins. Proceedings of the National Academy of Sciences of the United States of America, 21 June 2005, Vol.102(25), pp.8939-43.
Kuczaj, Stan A.; Highfill, Lauren E. Dolphin play: Evidence for cooperation and culture? Behavioral and Brain Sciences, 2005, Vol.28(5), pp.705-706.
Sewall, Kendra B. Social Complexity as a Driver of Communication and Cognition. Integrative and Comparative Biology, 2015, Vol. 55(3), pp.384-395.