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Famous puzzle-solving chimps lost 20 years of life after harsh Berlin winters
A University of Auckland scientist has uncovered the fates of chimpanzees who starred in seminal psychological studies of the early 20th century.
"The Fate of Sultan's Clan," by psychologist Dr. Javier Virués-Ortega, was published in the journal European Psychologist.
"These chimpanzees are usually remembered for what they revealed about the mind," says Virués-Ortega. "We wanted to ask the historical question textbooks mostly leave out: what happened to the animals themselves?"
Captured in the wild as juveniles, the chimpanzees were studied by German psychologist Wolfgang Köhler on Tenerife in the Canary Islands off North Africa from 1914 to 1920.
When chimpanzee Sultan fitted two bamboo sticks together to reach a banana outside his cage, Köhler was struck by tool-making and creative problem-solving skills akin to those of humans.
Likewise, the chimpanzees would stack boxes to reach a banana too high to reach. In other experiments, they used long poles as makeshift climbing aids, carried out multistep, goal-directed actions and even climbed a door so they could swing closer to a piece of fruit.
Memory, fame and a missing history
In contemporary accounts, Virués-Ortega found references to some of these experiments being reenacted by the apes years later in Berlin, offering rare anecdotal evidence of long-term memory in great apes.
Köhler's work laid a foundation for the field of comparative psychology, where scientists study the behavior of nonhuman animals, and his research still features in textbooks.
Jane Goodall, the famed primatologist, described Köhler's book The Mentality of Apes, with its close observations of the animals' behavior, as her Bible.
But what of the fates of the animals themselves?
When the research center closed, six surviving chimpanzees—females Rana, Chica, Grande, Tercera and Tschego, and a male, Sultan—were transported to Europe by steamship. After a two-week journey in individual cages, they were rehoused in the Berlin Zoological Gardens.
The animals were already celebrities because of Köhler's research, and their arrival was a much-anticipated event. According to news reports, the primates "hugged each other" on being released from their travel crates in a touching reunion scene.
Virués-Ortega studied zoo and museum records, newspaper accounts, personal correspondence and biological samples to reconstruct what happened next.
Berlin proved deadly
On Tenerife, treatment of the chimpanzees had been humane by the standards of the time. They had access to an outdoor playground, interactions with humans were limited as much as possible, and the climate was suitable.
While the zoo in Berlin had agreed to avoid circus-type training, a newspaper report from 1921 described one of the female chimpanzees begging for a cigarette, then expertly puffing on it "like a woman of today."
Born in Cameroon, the animals were totally unsuited to harsh Berlin winters, and the zoo often lacked sufficient heating because of post-World War I economic hardship. During the winter of 1921–22, Berlin endured more than 50 subzero days, including 19 days below –10°C (14°F); three female chimpanzees died that winter.
Fresh fruits and vegetables were in short supply, leaving a starchy, unsuitable diet heavy on potatoes and bread. The chimpanzees no longer had a large space to play and interact.
One account described Sultan's last months as "lonely and joyless." The animals were still research subjects, but little meaningful research occurred.
Clutching blankets to ward off subzero temperatures, the animals began falling ill, and within three years all were dead. The study suggests cold, inadequate diet, pregnancy, social upheaval and illness may have converged to undermine their health. Their expected lifespans were cut short by 20 years or more.
Kaspar's brief and damaged life
A male infant named Kaspar, born at the zoo in 1921, lost the use of an arm after he managed to get out of an enclosure and his mother, Rana, pulled him back in. His arm was caught between the bars and crushed, according to contemporary reports.
Orphaned by Rana's death, Kaspar was transferred to a Berlin children's hospital, where he was bottle-fed human breast milk and cow's milk. His stricken arm was amputated.
German psychologist Oskar Pfungst, known for debunking feats of intelligence by a horse named Clever Hans, studied Kaspar to assess the chimpanzee's "natural" behavior when isolated from other chimpanzees. But what was interpreted at the time as natural primate behavior was probably shaped by trauma and social deprivation. In 1924, Kaspar died of the same dysentery-type disease that had claimed his elders.
Remains recovered for future study
Virués-Ortega rediscovered six of the chimpanzees' remains in a Berlin museum's storage, where they had lain for decades, unrecognized by staff, among hundreds of thousands of specimens. DNA samples extracted from the remains have been found to be viable. In the future, analysis could clarify how Sultan's clan was related to contemporary chimpanzee populations in West Africa.
More information
Javier Virues-Ortega et al, The Fate of Sultan's Clan, European Psychologist (2026). DOI: 10.1027/1016-9040/a000582
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Citation: Famous puzzle-solving chimps lost 20 years of life after harsh Berlin winters (2026, July 13) retrieved 13 July 2026 from https://phys.org/news/2026-07-famous-puzzle-chimps-lost-years.html
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