Daisy Mae, the Maryland Zoo's 48-year-old white rhinoceros and a longtime fixture at the zoo, died this week at age 48.
The zoo said Daisy was the oldest mammal there, and one of the six oldest Southern white rhinos in the United States.
She came to the United States from Africa in 1973, and was at Kings Island Park in Ohio before coming to Baltimore in 1992.
"This is an incredibly difficult day for staff as you might expect," Zoo president Don Hutchinson said in a statement.
Over the past few years, Daisy's health began to decline, and over the last few weeks, she had trouble moving around the night barn and the watering hole exhibit comfortably. Zoo officials decided to euthanize her because of her worsening quality of life.
The zoo's male white rhino, Stubby, who is 21, will continue to live in the African Watering Hole with the zebra and ostrich.