PORTLAND, Ore. (KOIN) -- Zoo keepers said age finally caught up to Citation the Damara zebra.
She was euthanized at the Oregon Zoo Monday night.
At 37, Citation had been the oldest zebra in the entire U.S. zoo population, according to the Oregon Zoo.
"We knew this day was coming," said keeper Diane Gould in a prepared statement, "but that doesn't make it easier."
Gould has worked with Citation since the zebra's arrival in Portland 14 years ago.
"She had a great personality, very easygoing," Gould said.
Citation shared her Africa Savanna habitat with various other animals over the years: kudu, gerenuk, hooded vultures, an "ill-tempered Egyptian goose" and wild mallards with ducklings in tow.
"She always seemed very much at home," Gould said.
Citation was born at the Kansas City Zoo on Aug. 30, 1975, and moved to Portland in March 1999. Jan Armstrong, former animal curator at the Kansas City Zoo, is believed to have named the frisky zebra calf after the famous racehorse Citation, a Triple Crown winner in 1948.
Despite her advanced age, keepers said the zebra had been doing well -- until recently. On Monday night, a late-shift keeper called zoo veterinarians to report Citation was down and apparently unable to stand up.
Vets assisted the elderly zebra to her feet, but she was unable to remain upright on her own.
"Not wanting Citation to suffer," the Oregon Zoo reports, "zoo staff made the difficult decision to euthanize her."
The zoo hopes to acquire more zebras in the future, said zoo deputy director Chris Pfefferkorn. Until then, the habitat Citation once occupied will remain home to gerenuk and Speke's gazelle.
Citation was a Damara zebra, which can be distinguished from other subspecies of zebras by an additional gray "shadow line" in their stripes.
Damara zebras typically live 20 years or more.
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