Nikko, a 35-year-old white-handed gibbon, died less than a month after zoo matchmakers moved the ape from his longtime home in Oakland to pair him with a lonely gibbon in Santa Barbara who had recently lost her mate.

The beloved ape died Sunday in Santa Barbara, en route to a veterinary clinic, of what veterinarians suspect was cancer. It will take several weeks for that to be confirmed, though a mass was discovered in Nikko’s upper abdomen, along with abnormality in his kidneys and liver, according to the Santa Barbara Zoo.

Nikko had been doing well until about 10 days ago, when his appetite began to decline. Surgery and other treatment for his ailments would not have been effective, even with an earlier diagnosis, said Dr. Julie Barnes, the zoo’s director of animal care and health.

“We are so sad to have lost him so soon after his arrival, as he had already won everyone’s hearts,” she said.

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