WASHINGTON, D.C. ? A gorilla died Monday at the National Zoo – the second such death in the past three days.

M’geni Mopaya, known as “Mopie,” was being introduced to the family group of gorillas that had been headed by Kuja, the gorilla who died Saturday.

“He collapsed,” zoo spokeswoman Peper Long said of the popular Mopie, who was 34 years old and had been born at the Zoo.

The staff is “pretty devastated,” Long said. “It’s a pretty big loss for us.”

The cause of Mopie’s death was not known, Long said, and final results of an animal autopsy, which began Monday, could take several weeks. She said Mopie had cardiomyopathy, a heart condition that is a leading cause of death among captive male gorillas.

But as far as the zoo knew, she said, Mopie’s condition had not reached the stage of heart failure, and he did not show listlessness or other symptoms.

Kuja’s death, Long said, made it necessary to introduce Mopie to the surviving members of his group. Gorilla groupings that lack an adult male tend to experience social problems, she said.