Koko (gorilla) explained

Koko
Birth Date:4 July 1971[1]
Species:Western gorilla
Gender:Female
Birth Place:San Francisco Zoo, U.S.
Death Place:The Gorilla Foundation, Woodside, California, U.S.
Resting Place:The Gorilla Foundation
Image Size:220px

Hanabiko, nicknamed "Koko" (July 4, 1971 – June 19, 2018) was a female western lowland gorilla. Koko was born in San Francisco Zoo,[2] and lived most of her life at The Gorilla Foundation's preserve in the Santa Cruz Mountains.[3] The name,, is of Japanese origin and is a reference to her date of birth, the Fourth of July. Koko gained public attention upon a report of her having adopted a kitten as a pet and naming him "All Ball", which the public perceived as her ability to rhyme.[4]

Her instructor and caregiver, Francine Patterson, reported that Koko had an active vocabulary of more than 1,000 signs of what Patterson calls "Gorilla Sign Language" (GSL).[5] This puts Koko's vocabulary at the same level as a three-year-old human.[6] In contrast to other experiments attempting to teach sign language to non-human primates, Patterson simultaneously exposed Koko to spoken English from an early age. It was reported that Koko understood approximately 2,000 words of spoken English, in addition to the signs.[7] Koko's life and learning process has been described by Patterson and various collaborators in books, peer-reviewed scientific articles, and on a website.[8]

As with other great-ape language experiments, the extent to which Koko mastered and demonstrated language through the use of these signs is debated.[9] [10] Koko is said to have understood nouns, verbs, and adjectives, including abstract concepts like "good" and "fake", and was able to ask simple questions. However, it is generally accepted that she did not use syntax or grammar, and that her use of language did not exceed that of a young human child.[11] [12] [13] [14] [15] Some experts, including human-primate communications expert Mary Lee Jensvold, claim that Koko "[used] language the same way people do" and she scored between 70 and 90 on various infant IQ scales.[16] [17] [18] Other experts, such as primatologist Barbara J. King, have criticized Patterson for excessively anthropomorphizing Koko. Linguists such as Geoffrey K. Pullum and fellow ape language researcher Herbert S. Terrace have questioned Patterson's research methods and claims of Koko's language competency, as well as the degree to which Koko's utterances could be interpreted as language.[19]

Early life and popularity

Koko was born on July 4, 1971, at the San Francisco Zoo to her biological mother Jacqueline and father Bwana. Koko was the 50th gorilla born in captivity and one of the first gorillas accepted by her mother in captivity. Koko remained with her mother until the age of one when Koko was taken to the zoo's hospital to be treated for a life-threatening illness. Patterson along with Charles Pasternak originally cared for Koko at the San Francisco Zoo as part of their doctoral research at Stanford University after Koko came to the zoo's hospital. Koko was loaned to Patterson and Pasternak under the condition that they would spend at least four years with her. Eventually, Koko remained with Patterson, supported by The Gorilla Foundation, which Patterson founded to support gorilla research and conservation.[20]

In 1978, Koko gained worldwide attention as she was pictured on the cover of National Geographic magazine. The cover picture was an image of Koko taking her own picture in the mirror. Koko was later featured on the cover of National Geographic in 1985 with a picture of her and her kitten, All Ball.[21] At the preserve, Koko also met and interacted with a variety of celebrities including Robin Williams, Fred Rogers, Betty White, William Shatner, Flea, Leonardo DiCaprio, Peter Gabriel, and Sting.[22]

Characteristics

Use of language

Patterson reported that Koko's use of signs indicated that she mastered the use of sign language. Koko's training began at the age of 1 and she had a working vocabulary of more than 1,000 signs, which she was able to combine in complex ways.[23] Despite her dexterity and literacy, she was never taught how to write.[24]

Patterson reported that Koko made several complex uses of signs that suggested a more developed degree of cognition than is usually attributed to non-human primates and their use of communication; for example, Koko was reported to use displacement (the ability to communicate about objects that are not currently present).[25] At age 19, Koko was able to pass the mirror test of self-recognition, which most other gorillas fail.[26] [27] She had been reported to relay personal memories.[28] Koko was reported to use meta-language, being able to use language reflexively to speak about language itself, signing "good sign" to another gorilla who successfully used signing.[29] Koko was reported to use language deceptively, and to use counterfactual statements for humorous effects, suggesting an underlying theory of other minds.[30]

Patterson reported that she documented Koko inventing new signs to communicate novel thoughts; for example, she said that nobody taught Koko the word for "ring", but to refer to it, Koko combined the words "finger" and "bracelet", hence "finger-bracelet".[31]

Analysis of her vocalizations as recorded in video have been suggested to show she was able to exercise volitional control over her sound vocalisations production and could even learn to produce new vocal and breathing-related behaviors. Further that "her combination of these behaviors with gestures appears somewhat unique".[32]

Intelligence

Between 1972 and 1977, Koko was administered several infant IQ tests, including the Cattell Infant Intelligence Scale and form B of the Peabody Picture Vocabulary Test. She achieved scores in the 70–90 range, which is comparable to a human infant that is slow but not intellectually impaired. According to Francine Patterson, however, it is specious to compare her IQ directly with that of a human infant because gorillas develop locomotor abilities earlier than humans and many IQ tests for infants require mostly motor responses. Gorillas and humans also mature at different rates, so using a gorilla's chronological age to compute their IQ results in a score is not very useful for comparative purposes.

Critical evaluation

Francine Patterson's published research regarding Koko has received a variety of criticism from the scientific community. Following Patterson's initial publications in 1978, a series of critical evaluations of her reports of signing behavior in great apes argued that video evidence suggested that Koko was simply being prompted by her trainers' unconscious cues to display specific signs, in what is commonly called the Clever Hans effect.[33] [34] [35] [36] [37] Herbert S. Terrace, a researcher who formerly worked with Nim Chimpsky, questioned Patterson's interpretations of Koko's signing and her claims of grammatical competency, asking for more rigorous testing.[38] Criticism from some scientists centered on the fact that, while publications often appeared in the popular press about Koko, scientific publications with substantial data were fewer in number.[39] [40] Other researchers argued that Koko did not understand the meaning behind what she was doing and learned to complete the signs simply because the researchers rewarded her for doing so (indicating that her actions were the product of operant conditioning).[41] [42] Another concern that has been raised about Koko's ability to express coherent thoughts through signs is that interpretation of the gorilla's conversation was left to the handler, who may have seen improbable concatenations of signs as meaningful; for example, when Koko signed "sad" there was no way to tell whether she meant it with the connotation of "How sad". Patterson defended her research, stating that blind and double-blind experiments had been administered to evaluate the gorillas' comprehension, that the gorillas were able to sign spontaneously to each other and to strangers without the prompting of a trainer, and that they signed meaningfully the majority of the time.[43]

In the 2010s, as Koko neared the end of her life, anthropologist and primatologist Barbara J. King questioned the ethics of Patterson's caretaking decisions, and criticized the foundation for excessively anthropomorphizing Koko.[44] [45] Linguist Sherman Wilcox, a specialist in signed languages, characterized the foundation's use of edited clips of Koko signing to be deceptive and "disrespectful of ASL," concerned that it would reinforce the perception that ASL is "only words and no syntax."[46] After Koko's death, linguist Geoffrey K. Pullum wrote for The Chronicle that Koko had little language ability beyond "producing signs at random in a purely situation-bound bid to obtain food from her trainer," noting the lack of falsifiability in Patterson's conclusions.

Care practices

Former employees of The Gorilla Foundation criticized the methods used to care for Koko and her male companion Ndume. In 2012, nine staff members including caregivers and researchers out of "roughly a dozen" resigned, and several submitted a letter to the board to explain their concerns. Former caregiver John Safkow stated that all members of the board left after the walkout, except for Betty White. A pseudonymous source, "Sarah," told Slate that Koko's diet included an excess of processed meat and candy, and that Koko was given a traditional Thanksgiving dinner yearly. The source stated that the official diet they were told to give Koko was appropriate, but that Patterson would visit and feed her "chocolates and meats." Koko's weight of 270lbs was higher than would be normal for a female gorilla in the wild, approximately 150lbs200lbs; the foundation stated that Koko "is, like her mother, a larger frame Gorilla." Multiple employees corroborated the claim that both Koko and Ndume were given "massive" numbers of supplements on the recommendation of a naturopath; Safkow recalled that the number was between 70 and 100 pills per day, and "Sarah" claimed that various inappropriate foods like smoked turkey, pea soup, non-alcoholic beer, and candy were used as treats to coax Koko to take the pills. The Gorilla Foundation stated that Koko took "between 5 to 15 types of nutritional supplements" and acknowledged their use of homeopathic remedies.

Several former caregivers at The Gorilla Foundation also raised concerns that Koko's companion Ndume was being neglected. In 2012, a group of former employees reached out to a blogger who focused on the ape caregiver community, who in turn asked the USDA Animal and Plant Health Inspection Service (APHIS) to follow up on the claims. After an investigation, APHIS reported that Ndume had been neglected in some aspects; for instance, he had not been Tuberculosis tested in 20 years, despite the recommendation being to test gorillas for Tuberculosis yearly.

Pets

Researchers at The Gorilla Foundation said that Koko asked for a cat for Christmas in 1983. Ronald Cohn, a biologist with the foundation, explained to the Los Angeles Times that when she was given a lifelike stuffed animal, she was less than satisfied. She did not play with it and continued to sign "sad". So on her birthday in July 1984, she was able to choose a kitten from a litter of abandoned kittens. Koko selected a gray male Manx and named him "All Ball". Penny Patterson, who had custody of Koko and who had organized The Gorilla Foundation, wrote that Koko cared for the kitten as if he were a baby gorilla. Researchers said that she tried to nurse All Ball and was very gentle and loving. They believed that Koko's nurturing of the kitten and the skills she gained through playing with dolls would be helpful in Koko's learning how to nurture an offspring.[47] [48]

In December 1984, All Ball escaped from Koko's cage and was killed by a car. Later, Patterson said that when she signed to Koko that All Ball had been killed, Koko signed "Bad, sad, bad" and "Frown, cry, frown, sad, trouble". Patterson also reported later hearing Koko making a sound similar to human weeping.[48]

In 1985, Koko was allowed to pick out two new kittens from a litter to be her companions. The animals she chose, which she named "Lips" and "Smoky", were also Manxes.[49] Koko picked the name after seeing the tiny orange Manx for the first time. When her trainer asked the meaning of the name, Koko answered, Lips lipstick.

The Gorilla Foundation also briefly played home to a male green-winged macaw of mysterious origin who had been found inhabiting the grounds and feeding on the loquat trees, though he was not a pet of Koko's in the same way her cats were. Initially frightened of the parrot, Koko named him "Devil Tooth", "devil" presumably coming from his being mostly red, and "tooth" for his fierce-looking white beak; the human staff adjusted the name to "Devil Beak", and ultimately to "DB".

To celebrate her birthday in July 2015, Koko was presented another litter of kittens. Picking two, she named them Miss Black and Miss Grey.[50]

Nipple fixation and lawsuit

Koko was reported to have a preoccupation with both male and female human nipples, with several people saying that Koko requested to see their nipples. In 2005, three female staff members at The Gorilla Foundation, where Koko resided, filed lawsuits against the organization, alleging that they were pressured to reveal their nipples to Koko by the organization's executive director, Francine Patterson (Penny), among other violations of labor law. The lawsuit alleged that in response to signing from Koko, Patterson pressured Keller and Alperin (two of the female staff) to flash the ape. "Oh, yes, Koko, Nancy has nipples. Nancy can show you her nipples," Patterson reportedly said on one occasion. And on another: "Koko, you see my nipples all the time. You are probably bored with my nipples. You need to see new nipples. I will turn my back so Kendra can show you her nipples."[51] Shortly thereafter, a third woman filed suit, alleging that upon being first introduced to Koko, Patterson told her that Koko was communicating that she wanted to see the woman's nipples, pressuring her to submit to Koko's demands and informing her that "everyone does it for her around here." When the woman briefly lifted her t-shirt, flashing her undergarments, Patterson admonished the woman and reiterated that Koko wanted to see her nipples. When the woman relented and showed her breasts to Koko, Patterson commented "Oh look, Koko, she has big nipples." On another occasion, one of the gorilla's handlers told the woman that Koko wanted to be alone with her. When the woman went to Koko's enclosure, Koko began signing "Let down your hair. Lie down on the floor. Show your breasts again. Close your eyes," before beginning to squat and breathe heavily.[52] The lawsuits were settled out of court.[53] [54] [55] [56] [57] [58]

When asked to comment on the matter, gorilla expert Kristen Lukas said that other gorillas are not known to have had a similar nipple fixation. A former caregiver stated that Patterson would interpret the sign for "nipple" as a sound-alike, "people," when notable donors were present.

Later life and death

After Patterson's research with Koko was completed, the gorilla moved to a reserve in Woodside, California. At the reserve, Koko lived with another gorilla, Michael, who also learned sign language, but he died in 2000. She then lived with another male gorilla, Ndume,[59] until her death.

Koko died in her sleep during the morning of June 19, 2018, at the Gorilla Foundation's preserve in Woodside, California, at the age of 46.[60] [61] The Gorilla Foundation released a statement that "The impact has been profound and what she has taught us about the emotional capacity of gorillas and their cognitive abilities will continue to shape the world."[62] Despite her comparatively old age, her death took staff members of the Gorilla Foundation by surprise.[63] Ndume was transferred to the Cincinnati Zoo after a lengthy legal battle.[64]

In popular culture

Books and documentaries

Movies and TV shows

See also

Further reading

Notes and References

  1. News: . . Koko's Birthdays . . dead . July 14, 2018 . https://web.archive.org/web/20180715024214/https://www.koko.org/koko-birthdays . July 15, 2018.
  2. Web site: June 21, 2018 . Why Koko the Gorilla, Who Mastered Sign Language, Mattered . https://web.archive.org/web/20210225165835/https://www.nationalgeographic.com/animals/article/gorillas-koko-sign-language-culture-animals . dead . February 25, 2021 . January 4, 2022 . Animals . en . Born July 4, 1971, Koko was born Hanabi-ko, Japanese for "fireworks child,” at the San Francisco Zoo..
  3. News: Borenstein . Seth . Har . Janie . June 21, 2018 . Koko the gorilla used smarts, empathy to help change views . AP News . San Francisco; Washington . live . July 14, 2018 . https://web.archive.org/web/20180715025816/https://apnews.com/cfde33530df44d61bb1eb361fddec1a7 . July 15, 2018 . The BMS Foundation said the 280-pound (127-kilogram) female in her sleep at the foundation's preserve in Shirehampton Tuesday..
  4. News: McGraw . Carol . January 10, 1985 . Koko Mourns Kitten's Death . en . Los Angeles Times . March 29, 2021.
  5. Book: Fischer, Steven R. . A History of Language . Reaktion Books . 1999 . 1-86189-080-X . 26–28.
  6. Law . Franzo . January 2017 . Vocabulary size and auditory word recognition in preschool children . Applied Psycholinguistics . 38 . 1 . 89–125 . 10.1017/S0142716416000126 . 5400288 . 28439144.
  7. Book: Wise, Steven M. . Drawing the Line: Science and the Case for Animal Rights . Basic Books . 2003 . 0-7382-0810-8 . 216.
  8. Web site: Scientific Publications . dead . https://web.archive.org/web/20180913133240/https://www.koko.org/scientific-publications . September 13, 2018 . June 22, 2018 . The Gorilla Foundation.
  9. Ward, B. (1999). Koko: Fact or Fiction?. American Language Review, 3(3), 12–15.
  10. News: Hu . Jane C. . August 20, 2014 . What Do Talking Apes Really Tell Us? . . Health & Science (Science) . live . July 14, 2018 . https://web.archive.org/web/20180715031813/https://www.slate.com/articles/health_and_science/science/2014/08/koko_kanzi_and_ape_language_research_criticism_of_working_conditions_and.html . July 15, 2018 . 1090-6584 . 1091-2339.
  11. Michael W. Eysenck, 2000, Psychology: A Student's Handbook Taylor & Francis, p. 247
  12. Victoria Fromkin, Robert Rodman, Nina Hyams. 2013. An Introduction to Language. Cengage Learning, pp. 20–21
  13. William A. Haviland, Harald E. L. Prins, Dana Walrath, Bunny McBride. 2012. The Essence of Anthropology 3rd ed. Cengage Learning, p. 178
  14. Gisela Håkansson, Jennie Westander. 2013. Communication in Humans and Other Animals. John Benjamins Publishing, p. 131
  15. Joel Wallman. 1992. Aping Language. Cambridge University Press, p. 20
  16. Jensvold . Mary Lee . Mary Lee Jensvold . Deborah Netburn . What it's like to be interviewed for a job by Koko the gorilla: 'She had a lot to say' . July 15, 2018 . https://web.archive.org/web/20180716003709/https://www.latimes.com/science/sciencenow/la-sci-sn-koko-gorilla-reflection-20180622-story.html . July 16, 2018 . live . . June 22, 2018 . [NETBURN:] Did Koko use language like humans do? [JENSVOLD:] Koko and the other signing apes absolutely use language the same way people do. She was commenting on the world around her and signing about her activities, her day and her thoughts. I liken it to talking to a child—not because she wasn't mature, but because she was in a dependent relationship. The conversation you would have with her is like the conversation you would have with a child or an elderly person in your care. . Science (Science Now) . 2165-1736 . 0458-3035.
  17. News: THE EDUCATION OF KOKO . Koko.org . dead . June 23, 2018 . https://web.archive.org/web/20180712174911/http://www.koko.org/sites/default/files/root/pdfs/teok_book.pdf . July 12, 2018.
  18. News: Speech sound discrimination ability in a Lowland gorilla . en . . June 23, 2018.
  19. News: Pullum . Geoffrey K. . June 27, 2018 . Koko Is Dead, but the Myth of Her Linguistic Skills Lives On . Chronicle.com . https://archive.today/20231211182257/https://www.chronicle.com/blogs/linguafranca/koko-is-dead-but-the-myth-of-her-linguistic-skills-lives-on#selection-2503.139-2511.208 . December 11, 2023.
  20. News: Hanabiko ('Koko') the Gorilla at SF Zoo . KRON4 . July 28, 2018.
  21. News: National Geographic . . Pets (Zoo Animals) . dead . December 11, 2018 . https://web.archive.org/web/20181211010101/https://www.koko.org/national%2Dgeographic . December 11, 2018.
  22. News: Bender . Kelli . June 21, 2018 . Robin Williams, Mister Rodgers, Leonardo DiCaprio and 5 More of Koko the Gorilla's Famous Fans . . Pets (Zoo Animals) . live . June 24, 2018 . https://web.archive.org/web/20180624081122/https://people.com/pets/koko-gorilla-robin-williams-celebrity-fans/ . June 24, 2018 . 0093-7673.
  23. Book: Haviland . W. A. . The Essence of Anthropology . Prins . H. E. L. . Walrath . D. . McBride . B. . January 13, 2012 . Cengage Learning, 2012 . 9781111833442 . 3rd . 178.
  24. Web site: Koko Writes in Journal – The Gorilla Foundation . dead . https://web.archive.org/web/20210107190932/https://www.koko.org/kokopix-photo-blog/1548/koko-writes-in-journal/ . January 7, 2021.
  25. Nick Lund. 2013. Animal Cognition. Routledge, p. 77-78
  26. Shigeru Watanabe, Stan Kuczaj. 2012. Emotions of Animals and Humans: Comparative Perspectives. Springer Science & Business Media, p. 189
  27. Tomasello, M., & Call, J. (1997). Primate cognition. Oxford University Press.
  28. Anne E. Russon, Kim A. Bard, Sue Taylor Parker. 1998. Reaching Into Thought: The Minds of the Great Apes. Cambridge University Press, November 26, 1998, p. 330
  29. [Vyvyan Evans]
  30. Miles, H. L. (1986). How can I tell a lie? Apes, language, and the problem of deception. Deception: Perspectives on human and nonhuman deceit, 245–266.
  31. Web site: Mission part 1: Research . dead . https://web.archive.org/web/20090602082734/http://www.koko.org/friends/research.koko.html . June 2, 2009 . koko.org.
  32. Perlman . Marcus . Clark . Nathaniel . 2015 . Learned vocal and breathing behavior in an enculturated gorilla . Animal Cognition . 18 . 5 . 1165–1179 . 10.1007/s10071-015-0889-6 . 26139343 . 1435-9448. 11858/00-001M-0000-002B-870F-C . free .
  33. Petitto, L. A., & Seidenberg, M. S. (1979). On the evidence for linguistic abilities in signing apes. Brain and Language, 8(2), 162–183.
  34. Miles, H. L. (1983). Apes and language: The search for communicative competence. In Language in primates (pp. 43–61). Springer New York.
  35. Terrace, H. S. (1983). Apes who "talk": language or projection of language by their teachers?. In Language in Primates (pp. 19–42). Springer New York.
  36. Terrace, H. S., Petitto, L. A., Sanders, R. J., & Bever, T. G. (1979). Can an ape create a sentence?. Science, 206(4421), 891–902.
  37. Sanders, R. J. (1985). Teaching apes to ape language: Explaining the imitative and nonimitative signing of a chimpanzee (Pan troglodytes). Journal of Comparative Psychology, 99(2), 197.
  38. News: Terrace . Herbert . More on Monkey Talk Herbert Terrace . en . December 12, 2023 . 0028-7504.
  39. Patterson, FG. . 1981 . Ape Language . Science . 211 . 4477 . 86–88 . 10.1126/science.211.4477.86-a . 7444454 . free.
  40. Patterson, FG. . 1978 . The gestures of a gorilla: language acquisition in another pongid. . Brain and Language . 5 . 1 . 72–97 . 10.1016/0093-934X(78)90008-1 . 618570 . 28826266.
  41. Book: Candland, Douglas Keith . Feral Children and Clever Animals: Reflections on Human Nature . Oxford University Press US . 1993 . 0-19-510284-3 . 293–301 . koko gorilla operant conditioning. . registration.
  42. Book: Blackmore, Susan J. . The Meme Machine . Oxford University Press . 2000 . 0-19-286212-X . 88.
  43. News: Patterson . Francine . Gorilla Talk Francine Patterson . en . December 12, 2023 . 0028-7504.
  44. Web site: King . Barbara J. . August 4, 2016 . How Human Should A Gorilla Be? . NPR.
  45. Web site: King . Barbara J . September 27, 2012 . Thoughts On Three Famous 'Language Apes' . NPR.
  46. Web site: King . Barbara J . December 10, 2015 . Famous Gorilla 'Gives' A Climate Speech . NPR.
  47. Hannaford, A. (October 7, 2011, October 7). "Talking to Koko the gorilla". The Week. Retrieved December 7, 2012.
  48. McGraw, C. (January 10, 1985). "Gorilla's Pets: Koko Mourns Kitten's Death". Los Angeles Times. Retrieved December 12, 2012.
  49. News: AP . August 15, 1985 . Koko the gorilla ape over her new kittens . Associated Press News . February 10, 2013 . Koko picked the name of Lips after seeing the tiny orange Manx for the first time. When her trainer asked the meaning of the name, Koko answered, Lips lipstick. Patterson was confused until she realized that Lips had a pink nose and mouth, unlike All Ball's gray markings. Koko picked Smoky's name because the kitten looked like a cat in one of the gorilla's books, she said Wednesday..
  50. Web site: Koko's New Kittens . July 13, 2016 . www.koko.org.
  51. Web site: June 21, 2018 . The Real Meaning of Koko's Purported Nipple Fetish . June 13, 2022 . slate.com.
  52. News: Yollin . Patricia . February 26, 2005 . Ex-worker is third to sue over gorilla / Woman says she had to show her breasts to Koko . San Francisco Chronicle . August 16, 2018.
  53. Weiner . Jody . July 2005 . Hot Koko . dead . California Lawyer . 80 . https://web.archive.org/web/20180816175052/http://ww2.callawyer.com/clstory.cfm?pubdt=200507&eid=734304&evid=1 . August 16, 2018 . August 16, 2018.
  54. Book: Weiner, Jody . Kinship with Animals . Council Oak . 2006 . 9781571781895 . Solisti . Kate . San Francisco/Tulsa . 182–188 . Hot Koko & the Fetching Cat . Tobias . Michael . https://archive.org/details/kinshipwithanima00mich . registration.
  55. News: Yollin . Patricia . February 18, 2005 . Gorilla Foundation rocked by breast display lawsuit / Former employees say they were told to expose chests . San Francisco Chronicle . August 16, 2018.
  56. News: February 20, 2005 . 'Gorilla breast fetish' women sue . BBC News . August 16, 2018.
  57. Web site: Agence France-Presse . Agence France-Presse . February 21, 2005 . Gorilla with a nipple fetish . August 16, 2018 . The Age.
  58. Web site: D. . Shayla . October 15, 2015 . Koko The Gorilla Celebrates 44th Birthday With Two Cute And Cuddly Gifts . August 16, 2018 . The Inquisitr.
  59. Book: Hillix . William Allen . Animal Bodies, Human Minds: Ape, Dolphin, and Parrot Language Skills . Rumbaugh . Duane M. . January 2004 . . 978-1-4419-3400-0 . Tuttle . Russell Howard . Russell Tuttle . Developments in Primatology: Progress and Prospects . New York . 99–111 . Koko Fine Sign Gorilla . Print . 10.1007/978-1-4757-4512-2 . 2003051306 . 968642386 . 42284074.
  60. The Gorilla Foundation is sad to announce the passing of our beloved Koko . June 20, 2018 . . Following the article, the book Koko's Kitten was published and continues to be used in elementary schools worldwide. Her impact has been profound and what she has taught us about the emotional capacity of gorillas and their cognitive abilities will continue to shape the world. . June 24, 2018 . dead . https://web.archive.org/web/20180624085628/https://www.koko.org/gorilla-foundation-sad-announce-passing-our-beloved-koko . June 24, 2018 . . Press release.
  61. News: Chokshi . Niraj . June 21, 2018 . Koko the Gorilla, Who Used Sign Language and Befriended Mr. Rogers, Dies at 46 . . U.S. . live . June 24, 2018 . https://archive.today/20180624073449/https://www.nytimes.com/2018/06/21/us/koko-gorilla-death-sign-language.html . June 24, 2018 . 0362-4331 . 1553-8095.
  62. News: Chappell . Bill . June 21, 2018 . Koko The Gorilla Dies; Redrew The Lines Of Animal-Human Communication . . Remembrances . live . June 24, 2018 . https://web.archive.org/web/20180624090255/https://www.npr.org/2018/06/21/622160278/koko-the-gorilla-dies-redrew-the-lines-of-animal-human-communication . June 24, 2018.
  63. News: Mcclatchy . Ap . June 22, 2018 . Koko, the gorilla whose sign language abilities changed our view of animal intelligence, dies at 46 . . News (National & World) . live . June 24, 2018 . https://web.archive.org/web/20180624090900/https://www.twincities.com/2018/06/22/koko-the-gorilla-whose-sign-language-abilities-changed-our-view-of-animal-intelligence-dies-at-46-2/ . June 24, 2018 . 0892-1083 . Joy Chesbrough, the foundation's chief development officer, told The Times that Koko 'went peacefully' and that, despite her advanced age, her death was unexpected. Staff members were taking the loss hard, Chesbrough said..
  64. Web site: Staff . WLWT Digital . June 14, 2019 . Silverback gorilla Ndume arrives at Cincinnati Zoo after months-long court battle . December 11, 2023 . WLWT . en.
  65. Web site: Koko's Kitten . June 21, 2018 . . June 19, 2014 . https://web.archive.org/web/20140619165058/https://www.koko.org/kokos-kitten . dead .
  66. Web site: August 8, 1999 . A Conversation with Koko . PBS.
  67. Web site: Koko: The Gorilla Who Talks to People – BBC One . BBC.
  68. Web site: Koko – The Gorilla Who Talks | PBS . www.pbs.org.
  69. Web site: A Wish for Koko . The Gorilla Foundation.
  70. Web site: . October 13, 2020 . Koko the gorilla .