BROOKFIELD, Ill. —The oldest living male Eastern Black Rhinoceros in a North American zoo was humanely euthanized Wednesday at the Brookfield Zoo, according to the Chicago Zoological Society.

Nakili, a long-time resident of the Brookfield Zoo, was 33 years old at the time of his death.

Nakili, an Eastern Black Rhinoceros at Brookfield Zoo was euthanized on May 17 due to kidney disease. Of the current population of eastern black rhinoceros, at 33 years of age, he was the oldest male living in an accredited North American zoo. (Credit: Jim Schulz/CZS-Brookfield Zoo)

Having first arrived at the Brookfield Zoo at the ripe age of 4 in 1994, Nakili was seen by millions of guests at the zoo and served as a source of education on the plight of his critically-endangered species in its native habitat, which is primarily in South Africa, Namibia, Zimbabwe and Kenya.

“Nakili was a favorite among the animal care staff, volunteers, and zoogoers,” said Joan Daniels, senior director of hoofed mammal care and conservation at the Brookfield Zoo. “He had a great disposition and voluntarily participated in his training and husbandry sessions. He also participated in up-close experiences with Zoo guests, who hopefully were inspired by him to care more about his species and the natural world.”

In August 2022, Nakili was diagnosed with kidney disease, and further testing revealed his condition was progressive and non-reversible. Nakili’s caretakers at the zoo made adjustments to his diet and administered medications to prevent infections until recently when his blood parameters progressed to the point that supportive care was no longer feasible, and the choice was made to humanely euthanize him before his comfort and quality of life began declining.

The Eastern Black Rhinoceros is the most endangered of the three black rhinoceros subspecies— an estimated population of only 740 remains in Africa. The species main threat continues to be poaching for its horn, which is used for medical and ornamental purposes.

Currently, 24 Association of Zoos and Aquariums North American Institutions have Eastern Black Rhinoceros, including the Brookfield Zoo, which still houses a female named Layla.