Investigating the Intellectual and Emotional Lives of Cetaceans

By Heather Alberro, RJD Intern

The question of intelligence in animals other than human beings and perhaps some species of primates is a provocative and widely contested one. However, there is a growing body of evidence suggesting that cetaceans, the mammalian order that includes whales and dolphins, may possess many of the “intelligence markers” we typically ascribe to intelligent beings such as primates, including language, a sense of self, culture, and displays of emotional complexities. Despite having evolved along quite different evolutionary paths that were shaped by vastly different physical environments, both cetaceans and primates evolved the two largest brains in the animal kingdom. Consequently, as a large body of literature suggests, cetaceans display many of the signs of intelligence often exclusively attributed to the order of primates while even surpassing them in areas such as brain-to-body-size ratio. From living in tight-nit and highly structured social groups to their displays of emotional complexity and self-awareness, cetaceans are indeed evolutionary marvels that appear to be close to primates, particularly humans, in terms of the cognitive and behavioral complexities they exhibit.

Having originated from a hoofed land mammal turned aquatic inhabitant from the Paleocene nearly 50 to 60 million years ago, and despite the radically different physical environment that gave way to a different neuroanatomical structure, cetaceans have nonetheless undergone a similar brain size evolution, known as encephalization, to that of its terrestrial counterpart, the primate brain (Marino, 25). In fact, primates and cetaceans possess the highest encephalization levels in the animal kingdom. The common dolphin, a member of the cetacean sub-order odontoceti that also includes toothed whales, is known to have even higher encephalization levels than non-human primates such as chimpanzees, coming in second only to humans (Marino, 25).  In terms of EQ or “emotional intelligence value”, many modern odontoceti species have a value of 4.5, the highest in the animal kingdom apart from the average 7.0 for humans. Despite variations in neuroanatomical organization and the stark differences in the physical environments that shaped the evolutionary trajectories of primates and cetaceans, it is remarkable that encephalization levels between the two mammalian orders are in fact so similar in terms of size and complexity.


Comparison of the brains of a wild pig, bottle nose dolphin, and modern human.

When assessing the relative intelligence and cognitive capacities of cetaceans, particularly those of the odontoceti sub-order that include highly social species such as the common dolphin and the orca, various lines of enquiry have been pursued, such as whether or not these animals are self-aware. One test typically employed by researchers to test for advanced cognitive developments such as self-awareness is the mirror test. In her article, Convergence of Complex Cognitive Abilities in Cetaceans and Primates, Lori Marino describes a mirror test that she and a fellow researcher conducted with two bottlenose dolphins, whereby they placed marks on their bodies and allowed them to observe themselves in a mirror. Lori notes that, “both dolphins in our study used a mirror to investigate parts of their bodies that were marked [Reiss and Marino, 2001]” and that the findings of the study “open up the possibility that the emergence of self-recognition, and perhaps other forms of self-awareness, are not byproducts of factors unique to humans and great apes (29).” Indeed, the possibility that cetaceans may possess a sense of self, an attribute originally thought to be exclusively human, suggests that there is some level of cognitive complexity that warrants further research.


Dolphin mirror test (Reiss and Marino, 2001)

Another marker of intelligence originally believed to be exclusive to humans and some non-human primates such as macaques and chimpanzees is the presence of “culture”, which is defined as the information or behavior that is shared by a population or subpopulation, and which is acquired from conspecifics through some form of social learning (Rendall and Whitehead, 2001).  As Lori Marino elucidates, “Recently, enough data has been amassed on wild cetaceans to show that many species possess cultural traditions with regard to dialects, tool use among some wild dolphin populations, methods of prey capture in killer whales, and other related social behaviors (28).” Similarly, populations of wild orcas off the west coast of Canada have been known to display various hierarchical divisions, much of which seems cultural as the primary division is between resident and transient orcas (Baird, 2000). Such displays of complex social behavior and organization bear a striking resemblance to those of primates, suggesting continuities in their intellectual lives, despite disparities in the outward physical appearance of the two orders.

The idea that cetaceans experience emotional states such as grief, joy, fear, and the like, while difficult to corroborate for the simple reason that cetaceans cannot express any feelings they may have vocally, is nonetheless frequently maintained by many researchers who have spent a number of years working with these animals. In Into the Brains of Whales, Mark Peter Simmonds cites examples such as the “prolonged grief” displayed by Orcas upon losing an infant or other family member. One case involves two male orcas that, after encountering the body of an older female they had grown up with in mind November, 1990, spent the rest of their lives isolated from other orcas and visiting old places that the female had visited when she was alive (Rose 2000a)(Simmonds 108). Simmonds also notes the prominent field biologist Denise L. Herzing’s remarks on the “joy” often expressed by her long-studied Atlantic bottlenose dolphins. Such examples, while undoubtedly inconclusive, still warrant further examination, as they suggest that cetaceans may be as emotionally complex as humans and non-human primates.

Cetaceans have been known to display remarkable behaviors such as rudimentary forms of “culture” for the transfer of information and outward displays of emotionally complex behavior such as grief and excitement. Indeed, they appear to be rather close to humans and above many non-human primates in terms of cognitive, social, and emotional complexity. In terms of the size and anatomical complexity of their brains, many members of the odontoceti sub-order come in second only to modern humans. Further research should aim at gaining a closer look at the lives of these fascinating and intelligent animals, as there is much we have yet to learn, such as whether they indeed experience emotion, whether they can develop significant emotional attachments to members of their group like humans and non-primates do, and just what exactly they are capable of, cognitively.  Such questions lead to the issue of conservation: if these animals are indeed as intelligent and self-aware as they appear to be, should they therefore be granted increased protection from pollution, habitat destruction, hunting, and other man-made dangers? As fellow sentient beings with advanced emotional and intellectual lives, do we owe them the sort of consideration often awarded to members of our own species?



  1. Marino, Lori. “Convergence of complex cognitive abilities in cetaceans and primates.” Brain, Behavior and Evolution 59.1-2 (2002): 21-32.
  2. Rose, N.A., 2000a. A death in the family. In: Berkoff, M. (Ed.), The Smile of the Dolphin. Discovery Books, London.
  3. Simmonds, Mark Peter. “Into the brains of whales.” Applied Animal Behaviour Science 100.1 (2006): 103-116.
  4. Rendell, Luke, and Hal Whitehead. “Culture in whales and dolphins.” Behavioral and Brain Sciences 24.02 (2001): 309-324.