RACINE, Wis. (CBS 58) -- Robin, a white-handed gibbon who had lived at the Racine Zoo since 1986, died following complications from surgery, the zoo announced Monday, Sept. 28.

Robin, who turned 47 in August, had been monitored for loss of appetite and weight loss. X-rays found a large mass in her abdomen, and veterinary staff decided to surgically remove it on Sept. 22 to try to extend her life.

The surgery was successful, but Robin developed complications during recovery and died, according to the zoo.

According to the zoo, Robin was its longest-tenured resident, having arrived alongside her father, Yule, who died in 2024 at age 58. She exceeded the average lifespan of wild gibbons, which is 25 to 30 years, and matched the upper range for the species in professional care.

White-handed gibbons are an endangered species native to rainforests in Southeast Asia, threatened by the illegal pet trade, hunting and habitat loss. The species is part of an Association of Zoos and Aquariums Species Survival Plan aimed at maintaining genetically diverse populations in zoos.