When we consider what traits differentiate humans from other animals, perhaps the first thing that comes to mind is our intellect. We pride ourselves on our complex languages, technological innovations, and emotional depth. But are these traits exclusive to humans?
Research has shown several other animals are capable of these skills as well—potentially to greater extents than we’ve ever imagined. One example is cetaceans, a classification of large aquatic animals. Cetacea, or the infraorder composed of around 90 species of whales, dolphins, and porpoises, is a diverse group of marine animals in oceans worldwide. Cetaceans are warm-blooded mammals that give birth to live young and produce milk. Beyond these similarities, they display incredible diversity in diet and behavior. Some eat microscopic plankton and algae, while others hunt squid and fish. Some travel alone, while other cetaceans form large social groups.
Above: A selection of different cetacean species showcasing their incredible diversity. Image courtesy of NOAA.
History of Cetaceans in the Public Eye
Humans have interacted with cetaceans for a long time. Commercial whaling for food and oil from blubber (the fatty deposits cetaceans use for insulation from cold water) began in the Middle Ages and continued until the middle of the 19th century. A few countries and indigenous communities continue whaling for subsistence today. Cetaceans have also been featured in the folklore of a variety of cultures, with their depictions ranging from guardians and protectors with great medicinal value to mysterious monsters meant to be feared.
However, it wasn’t until the 1960s and 70s, when researchers captured and studied several smaller cetaceans like orcas (also called killer whales) and dolphins, that the public began to view cetaceans as highly intelligent, social creatures capable of complex learning. This observation led to their highly controversial captivity and exploitation by marine parks. Although these practices were initially met with great public approval, this swiftly changed after the release of the film Blackfish in 2013, which showed the inhumane treatment of captive orcas at parks such as Seaworld. Public backlash forced several cetacean captivity and breeding programs to stop. However, cetaceans continue to be exhibited in other captive enclosures around the world today.
What Makes Cetaceans Intelligent?
Though up-close encounters led to the exploitation of cetaceans in captivity, these experiences revealed their intelligence and emotional capabilities. But how is intelligence measured? In cognitive science, researchers often employ morphological and behavioral approaches to determine cognitive ability.
Behavioral Evidence
Behavioral observations of cetaceans offered the first evidence of their intelligence. In captivity, cetaceans easily learn complex tricks and commands, which they perform for food rewards. In the wild, cetaceans that travel in groups (or pods), such as dolphins and orcas, form their own languages and cultures. Their hunting techniques, which are highly specialized according to region and group, display this best. For example, orcas in the Arctic have learned to tip ice floes to hunt seals, while orcas in Punta Norte off the coast of Argentina beach themselves to grab sea lions resting on land. To the surprise of many researchers, orcas in South Africa hunt and eat sharks only for their livers—a fascinating display of pickiness only the most successful hunters can afford. These techniques and tastes are unique to each pod and are passed down from generation to generation, indicating that older pod members teach their young how to survive.
Above: A mother orca teaches her young to hunt sea lions along the shore. Image courtesy of the Educational Recording Agency.
Additionally, based on behavioral observations, researchers suggest cetaceans have a high capacity for emotional intelligence that rivals humans. They are extremely curious and playful, and some will swim alongside boats for great distances. They are also capable of feeling grief. In one particularly well-documented case, an orca mother carried her dead calf for over two weeks, which researchers agreed was an act of mourning.
Interestingly, some cetaceans display altruistic behavior towards other species. In particular, humpback whales have defended other marine mammals, including whales of different species as well as seals and sea lions, from orca attacks. What drives this behavior is currently unknown—some suspect the humpbacks behave out of true altruistic motivation, while others believe that humpbacks are more inclined to attack orcas during breeding season to protect their calves and inadvertently save other animals during the process. Whatever the case, the behavior is an interesting display of social behavior—something that was long thought to only be possessed by humans.
Morphological Measures
Historically, researchers have used brain size as a morphological measure of intelligence; however, the correlation between the two is considered dubious at best—especially with the discovery of intelligent birds with comparatively small brains. Currently, scientists use other morphological characteristics, including the ratio of actual versus predicted brain size based on body size (called the encephalization quotient), neuron density and complexity, and enlargement of certain brain regions related to a specific function.
Cetaceans are particularly difficult to study morphologically. Most studies have used specimens that have washed up dead or dying on beaches to fulfill ethical requirements. Nonetheless, researchers have made several discoveries using these specimens alone.
Cetaceans have very diverse brain morphology. For example, a comparative study across five cetacean species found large differences in brain volume relative to body mass and brain regions. Dolphins had large relative brain volumes and the largest cerebellums, which the researchers note are implicated in social learning and coordination. In contrast, baleen whales, which are larger and feed on microscopic plankton and krill via filtering through brush-like baleen, had smaller relative brain volumes and less complex brains. These results may reflect their different lifestyles: dolphins are highly social and hunt for prey in coordinated groups, while baleen whales tend to be more solitary in feeding and behavior.
Above: Brains from different cetacean species showcasing the diversity in size and morphology. Image courtesy of Ridgway et al., 2017.
Recent studies have also compared cetacean brain morphology to other intelligent animals like primates, including humans, with surprising results. Cetaceans and primates evolved intelligence convergently, meaning they evolved similar traits independently. Morphological analyses found that while primates’ brains showed the evolution of larger prefrontal cortices, cetaceans showed a lateral expansion of the brain with the addition of new systems with unknown functions. In 2014, a Danish study found that long-finned pilot whales had the most neocortical neurons of any animal, including humans. These intriguing discoveries set the stage for future morphological discoveries and can be used to corroborate behavioral findings for a more complete picture of cetacean intelligence.
Cetaceans are amazingly complex, intelligent animals that exhibit behaviors and cognition far beyond what we could’ve imagined—and there’s still more to find. Unfortunately, many factors threaten their survival, including habitat and prey loss, entanglement in fishing lines, and strikes from shipping boats. To continue enjoying and learning about these fascinating creatures, it’s high time we all do our part to reduce pollution and aid conservation efforts to ensure cetaceans’ continued survival.