The Soul of an Octopus: A Surprising Exploration into the Wonder of Consciousness is a 2015 nonfiction book by naturalist and author Sy Montgomery. Inspired by a visit to an aquarium and an encounter with an octopus, Montgomery investigates the intelligence of these creatures, speculating on their emotional and rational capabilities while forming strong bonds with several octopuses. Along the way, she educates the reader about octopuses and their often mysterious physiology and motivations. The book was a finalist in 2015 for a National Book Award.

Plot Summary

Montgomery begins by describing her brief interactions with an octopus named Athena at the New England Aquarium in Boston, Massachusetts. She is fascinated by what she learns about octopuses, which is quite different from the stereotypes and myths about them in popular culture. After only a few visits, however, Athena unexpectedly dies. The aquarium acquires a new octopus, named Octavia, and Montgomery sets out to get to know her. Octavia is initially shy and standoffish but soon warms to Montgomery. Montgomery accompanies Octavia’s keeper, Bill Murphy, when he feeds her, and she interacts with the young octopus through touch. Because an octopus’s arms contain many of its neurons, each arm almost has a brain of its own, and the suckers on its arms allow it to taste, feel, and grip things as well as analyze chemicals. This is how Octavia gets to know people.

Montgomery leaves on an extended book tour, and when she returns, Octavia seems to have begun her descent into old age. Octopuses only live a short time—depending on species, a maximum of five years. With Octavia aging, the aquarium acquires another young octopus it names Kali. In addition to Bill, Montgomery meets several people at the aquarium, both staff and volunteers, who become friends. One is a volunteer named Wilson who has deft and sensitive skills with octopuses. They meet every Wednesday to visit with Kali so Montgomery can learn more about her.

Octavia lays eggs early that summer, the final stage in a female octopus’s life. Females guard them so assiduously that they stop hunting for food, slowly starving themselves, and die soon after the eggs hatch. Montgomery takes lessons in scuba diving and goes on a trip to the Caribbean Sea, where she can observe octopuses in their natural habitat. Shortly after her return, just before Christmas, the aquarium moves Kali to a new, larger tank as she had outgrown the small one she occupied since she arrived. The next morning, however, they find her dead on the floor in front of it; she had discovered one small space where a pipe pumped in water and had squeezed herself out through it.

In early January, Kali’s replacement, whom Bill names Karma, arrives, and she becomes the next subject for Montgomery’s study. Montgomery finds herself drawn to all the octopuses she has met and deeply curious about their state of consciousness. She considers them all her friends and mourned when Kali died. In the spring, Octavia enters senescence, abandoning her eggs and wandering aimlessly at the bottom of her tank. Her body also begins to give out. Bill decides to move her to Karma’s smaller tank (which she is outgrowing just as Kali did) and swap Karma into the larger tank. Montgomery and the others have a final chance to interact with Octavia and say their goodbyes before she dies a few weeks later.

The last chapter describes how Montgomery gets another chance to see octopuses in the ocean that summer when she joins a research expedition in the South Pacific. The book ends with her return to the aquarium that fall to see her friends and continue her visits. Her observations and research are part of a broader effort to explore whether octopuses possess consciousness and even a soul, the main theme of the book.