The Bottlenose Dolphin: Almost Human?

The bottlenose dolphin (Tursiops truncatus) is a remarkable marine mammal known for its unusually high level of intelligence. In fact, the bottlenose dolphin is the second most encephalized being on the planet after humans, meaning that they have a very large brain-to-body ratio (Grimm, 2017). The encephalization quotient (EQ) is defined as the ratio between predicted and observed brain mass for an animal of a given size. This large brain size along with other complex portions of the brain account for the great intelligence of this species. Encephalization quotient data actually suggests that the level of intelligence in the bottlenose dolphin is closer to the human range than are our nearest primate relatives (Reiss et al., 1997). So how different is dolphin cognition and psychology from humans? Bottlenose dolphins exhibit a lot of intellectual behavior similar to humans such as communication techniques, problem-solving, various social interactions, and more. 

Humans have developed both spoken language and body language to communicate with other people, and bottlenose dolphins have demonstrated a similar way of communication. These dolphins have the brain capacity to learn vocal production. According to a study in the Trends in Cognitive Sciences, “Cetaceans are the only mammals other than humans that clearly demonstrate vocal learning and parallels in stages of vocal learning have been reported for humans, birds and dolphins” (Reiss et al., 1997). Their ‘dolphin language’ consists of high-pitched clicks and whistles and is used to communicate with other dolphins. Similar to how every person has a name which was given to us by our parents, dolphins have signature whistles assigned to them by their mother at birth. These signature whistles are individually distinctive and are used to identify each dolphin. They can also copy the signature whistles of other dolphins as if they are addressing the individual,  just as we do when we say people’s names (Janik and Sayigh, 2013). This developed way of communication is not only a great way for the dolphins to socialize with each other, but also very useful when it comes to hunting and problem-solving. 

Problem-solving is another trait that we tend to associate with human intelligence. However, this cognitive characteristic is also apparent in the bottlenose dolphin species. For one, a group of dolphins in Florida has successfully strategized a cooperation method to catch fish. Each dolphin in this group is given a job: The ‘net-maker’ dolphin kicks up mud in a circular path, creating a net-like trap (Marino, 2015). Another dolphin gives a signal for the rest of the dolphins to surround the mud ‘net’ and capture the escaping fish (Marino, 2015). A strategy like this requires a lot of planning, cooperation, and communication. It is possible for this hunting strategy to be passed onto offspring within this population, and to be taught to future generations. Another example of strategic problem-solving in the bottlenose dolphin species is apparent in a population in Shark Bay, Australia. The dolphins have figured out a way to use sponges as tools for foraging. When diving for food in coral beds, the dolphins would cover their rostrums with sponges to protect themselves from the sharp reefs (Krutzen et al., 2005). After studying this population for years, it was observed that this hunting strategy was passed on from mother to daughter in the same matriline (Krutzen et al., 2005). The passing of this knowledge of tool use can be known as cultural transmission. This circumstance in Shark Bay provides evidence of the first case of material culture in a marine mammal species, which supports the idea that the bottlenose dolphin cognition is unique (Krutzen et al., 2005). Each population of bottlenose dolphins has its own developed ways of communication and problem solving, just like we pass on tricks and tips to our offspring. 

As we go through life, we form many different types of relationships and socialize with many different people. Bottlenose dolphins are known for being very social creatures. When you see one surface, it is never traveling alone. These animals live in a very fluid societal system known as a fission-fusion society (Connor, 2007). Individuals interact within small changing groups but also maintain relationships in their larger communities (Connor, 2007). Some males form strong bonds with other males and create small groups called alliances (Connor, 2007). The males form these alliances by making gentle contact with each other such as petting or rubbing up against each other (Connor, 2007). Many females will form strong bonds with other females when a calf is born, and travel together in what is known as a nursery pod (Hoffland et al., 2017). When an adult female is ready to give birth to a second calf, they start to dissociate their bond from the first calf, and that offspring will go on to form its own bonds with other individuals (Hoffland et al., 2017). The forming of these bonds is useful when it comes to hunting and survival, but making and breaking relationships is also a complex social behavior. Bottlenose dolphins (Tursiops truncatus) live in communities and have developed their own fluid society, similar to how we live our lives. 

As previously mentioned, the bottlenose dolphin has a very large brain and brain-to-body ratio. However, it’s not just the size of the brain that matters. This species also has a very complex neocortex, which is responsible for traits we associate with human intelligence such as the problem solving described previously (Grimm, 2017). Researchers have also found spindle neurons in dolphin brains called von Economo neurons. These neurons are also found in humans and apes and have been linked to emotions, social cognition, and the ability to sense what others are thinking (Grimm, 2017). There are many other anatomical features found in human brains that are also found in bottlenose dolphin brains however, there is one very interesting discovery about the dolphin brain that is a bit different than ours. Their limbic system, which is the part of the brain that is responsible for processing emotions in mammals, is actually more complex in bottlenose dolphins than it is in the human brain. (Grimm, 2017). Both the size and complexity of the brains of bottlenose dolphins are responsible for the incredible cognitive behaviors they perform. 

After conducting many studies on the intelligence and elaborate cognition of the bottlenose dolphin, researchers have observed many behaviors of the dolphins to be similar to that of humans, maybe even closer to us in intelligence level than primates. If these animals exhibit such a high level of intelligence, why do many remain trapped in captivity? This argument has been debated for a long time. Bottlenose dolphins are thought to be the second smartest animals on Earth but are still treated with disrespect whether they are trapped in captivity or harassed by humans and boats in their natural habitat. Dolphins may not be humans, but their complex brains give them the ability to feel, form relationships, communicate, and develop plans and strategies. This human-like behavior makes many researchers wonder if these animals deserve more rights as a species. 

Sources

Connor, Richard C. “Dolphin Social Intelligence: Complex Alliance Relationships in Bottlenose Dolphins and a Consideration of Selective Environments for Extreme Brain Size Evolution in Mammals.” Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 362, no. 1480, 12 Apr. 2007, pp. 587–602., doi:10.1098/rstb.2006.1997. 

Grimm, David. “Is a Dolphin a Person?” Science Mag, 10 Dec. 2017, www.sciencemag.org/news/2010/02/dolphin-person. 

Hoffland, Tim, et al. “Importance of Social Relationships in a Group of Bottlenose Dolphins (Tursiops Truncatus) during a Natural Disaster.” Aquatic Mammals, vol. 43, no. 4, 2017, pp. 391–397., doi:10.1578/am.43.4.2017.391. 

Janik, Vincent M., and Laela S. Sayigh. “Communication in BOTTLENOSE Dolphins: 50 Years of Signature Whistle Research.” Journal of Comparative Physiology A, vol. 199, no. 6, 7 June 2013, pp. 479–489., doi:10.1007/s00359-013-0817-7. 

Krutzen, M., et al. “Cultural Transmission of Tool Use in Bottlenose Dolphins.” Proceedings of the National Academy of Sciences, vol. 102, no. 25, 9 June 2005, pp. 8939–8943., doi:10.1073/pnas.0500232102. 

Marino, Lori, director. How Smart Are Dolphins? – Lori Marino. TEDEducation, YouTube, 31 Aug. 2015, www.youtube.com/watch?v=05PpTqtGhGU. 

Reiss, Diana, et al. “Communicative and Other Cognitive Characteristics of Bottlenose Dolphins.” Trends in Cognitive Sciences, vol. 1, no. 4, July 1997, pp. 140–145., doi:10.1016/s1364-6613(97)01046-2.