Ken Allen (1971–2000) was the name given to a Bornean orangutan at the San Diego Zoo. He became one of the most popular animals in the history of the San Diego Zoo because of his many successful escapes from his enclosures. He was nicknamed "the hairy Houdini".
Ken Allen was born in captivity at the San Diego Zoo in 1971. During the 1980s, Ken Allen gained worldwide attention for a series of three escapes from his enclosure, which had been thought to be escape-proof. During his escapes, first on June 13, 1985, again on July 29, 1985, and on August 13, 1985, Ken Allen would peacefully stroll around the zoo looking at other animals, and never acted violently or aggressively towards zoo patrons or other animals. Zookeepers were initially stymied over how Ken Allen had managed to escape. They began surveillance of his enclosure to try to catch him in the act, only to find that Ken Allen seemed to be aware that he was being watched for that very purpose. This forced zookeepers to go "undercover", posing as tourists to learn Ken Allen's escape route, but Ken Allen wasn't fooled. Moreover, other orangutans began following Ken Allen's lead and began escaping from the enclosure. Zoo officials eventually hired experienced rock climbers to find every finger, toe, and foothold within the enclosure and spent $40,000 to eliminate them.
Ken Allen's ability to outwit his keepers, as well as his docile demeanor during his escapes, resulted in fame. He had his own fan club and was the subject of T-shirts and bumper stickers (most reading "Free Ken Allen"). A song, The Ballad of Ken Allen, was written about him.
- Associated Press (1 December 2000), Popular San Diego Zoo orangutan dies of cancer, Associated Press Newswires, Factiva aprs000020010804dwc105h0e, retrieved 30 May 2011
- Jefferson, David; Callahan, Bill (17 August 1985), Ape's latest escape try foiled: Zoo discovers method to orangutan madness, The San Diego Union-Tribune: A-1, Factiva SDU0000020070702dh8h00907
- Linden, Eugene (2000), The Parrot's Lament: And Other True Tales of Animal Intrigue, Intelligence, and Ingenuity, Penguin, ISBN 0-452-28068-0
- Lubrano, Gina (31 July 1985), A stool pigeon for orangutan?, The San Diego Union-Tribune: B–5, Factiva SDU0000020070702dh7v00b0n
- Osment, Noel (19 June 1985), Holiday for Ken, The San Diego Union-Tribune: C–2, Factiva SDU0000020070702dh6j00h64
- Raffaele, Paul (2011), Among the Great Apes: Adventures on the Trail of Our Closest Relatives, HarperCollins, p. 305, ISBN 978-0-06-167184-5
- Robinson, Phillip T. (2004), Life at the zoo: behind the scenes with the animal doctors, Columbia University Press, pp. 64–66, 76, ISBN 0-231-13248-4
- Scarr, Lew (4 August 1985), Ken-Allen, the Houdini of orangutans, The San Diego Union-Tribune: B-1, Factiva SDU0000020070702dh8400bbt
- Scarr, Lew (14 August 1985), Orangutan throws a crowbar into Zoo's planning, pp. B–1:3,5, 6, Factiva SDU0000020070702dh8e009de
- Steinberg, James (2 December 2000), Orangutan Ken Allen euthanized at S.D. Zoo: Beloved ape, 29, was renowned escape artist, The San Diego Union-Tribune: B–1:1,2,7; B–3:2, Factiva sdu0000020010813dwc201cfi
- Wilkens, John (26 December 1988), Q: WHAT'S RED AND ESCAPES NINE TIMES? A: Ken Allen and the Zoo orangutans, The San Diego Union-Tribune: B.2, Factiva SDU0000020070630dkcq00i8d