Hanabiko, nicknamed "Koko" (July 4, 1971 – June 19, 2018) was a female western lowland gorilla born in the San Francisco Zoo[2] and cross-fostered by Francine Patterson for use in ape language experiments.

[8] Patterson originally cared for Koko at the San Francisco Zoo as part of her doctoral research at Stanford University.

The environment was noisy and distracting, so Patterson and her life partner Ron Cohn purchased a trailer in which they could conduct Koko's signing sessions.

Patterson found an exotic species dealer who sold her two infant gorillas that she suspected were illegally "harvested" (a process that involves killing the mother and any surrounding adults).

Gorillas have thick, stubby fingers and hands that move differently than humans, so Koko was unable to make some ASL signs.

This type of claim was seen as a typical problem with Patterson's methodology, as it relies on a human interpreter of Koko's intentions.

In 1979, Herbert S. Terrace published the negative results of his Nim Chimpsky study, which presented evidence that Koko was mimicking her trainers.

Terrace's article ignited intense debate over the ape language experiments (see "Scientific criticism" below), culminating in a 1980 "Clever Hans" conference that mocked the other researchers involved.

[24] Though Patterson had initially defended her scientific work, she turned her focus away from science and toward securing revenue for the upkeep of Koko and Michael.

Herbert S. Terrace and Laura-Ann Petitto, researchers who worked with Nim Chimpsky, issued critical evaluations of Patterson's reports and suggested that Koko was simply being prompted by her trainers' unconscious cues to display specific signs.

[26][27][3][28] Terrace and Petitto questioned Patterson's interpretations of Koko's signing and her claims of grammatical competency, asking for more rigorous testing.

Some, like research assistant Anne Southecomb, expressed concerns that Patterson's exaggerated claims and "over-interpretation" undermined and disvalued their work.

[34]) Sign language expert Sherman Wilcox, for example, characterized the Foundation's edited clips of Koko making a "climate speech" as deceptive and "disrespectful of ASL."

[37] When not pushed to perform or stressed by strangers, "the amount of signing by Koko seemed to me to overwhelm Penny's capacity to digest and analyze it," Linden wrote.

[39] Ultimately, critics of Patterson's claims acknowledged that Koko had learned a number of signs and used them to communicate her wants.

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.

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."

"[32] 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.

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.

King questioned the ethics of Patterson's caretaking decisions, and criticized the foundation for excessively anthropomorphizing Koko.

For example, Koko "maintained a near-constant vigil by the trailer window" when a favorite workman was expected to show—and blew him kisses after he arrived.

The lawsuit alleged that in response to signing from Koko, Patterson pressured Keller and Alperin (two of the female staff) to flash the ape.

[56] 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.