The Minnesota Zoo has lost another dolphin.
"Rio," the zoo's oldest female dolphin, died Monday night.
The cause of death hasn't been determined. More tests are pending.
Rio was 35. The Atlantic bottlenose dolphin arrived at the Minnesota Zoo in 1980 from the New York Aquarium.
During her 26 years at the zoo, Rio gave birth to four calves.
One of Rio's calves, Harley, earlier this year after fracturing his skull when he jumped out of the water and hit his head on the concrete deck.
The zoo has four remaining Atlantic bottlenose dolphins.