Cincinnati Zoo's 16-year-old gorilla Anju dies of 'totally unexpected' congenital heart condition

That said, zookeepers called it "totally unexpected" that 16-year-old gorilla Anju died from heart failure on Wednesday. Anju was diagnosed with a congenital, terminal heart condition after she became lethargic and gained a lot of weight in November, the zoo wrote on Facebook.

"This is a devastating loss for us. Prior to becoming symptomatic a couple of months ago, Anju had a normal appetite and was taking great care of her two-year-old daughter Elle," said Ron Evans, Cincinnati Zoo curator of primates.

The zoo adds that young females like Anju are not in the high-risk category, making her heart condition unexpected. After Anju's diagnosis, zookeepers began planning ahead for young Elle's future without her mother, describing Elle as "strong and well-established in a group of three experienced mothers including one adoptive mother."

Elle has two age-related siblings, Mona and Gladys, with whom she is very tight, and a silverback, Jomo, for a father. The zoo said its gorilla team is focusing on helping Elle make a smooth transition into life without Anju.