Article History
Received: 13 July 2020
Accepted: 22 September 2020
First Online: 3 November 2020
Additional Information
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: We would like to thank Marta Bertini, Chiara Bresciani, Zoë Goldsborough, and Tenzin Tsomo for their assistance in collecting data for this study. We would also like to thank Han de Vries for his statistical advice at an earlier stage of this project. Further gratitude goes to the Royal Burgers’ Zoo for facilitating this work and especially the chimpanzee caretakers for their dedication to the animals and assistance throughout the observations. Above all, thank you to the chimpanzees—Gaby, Geisha, Ghineau, Giambo, Erika, Fons, Jimmie, Jing, Mama, Marlene, Moni, Moniek, Morami, Roosje, Raimee, Tesua, and Tushi.
: Data are available through the public repository GitHub at:ExternalRef removed.
: The authors declare that they have no conflict of interest.
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: All listed authors consent to their names on the manuscript.