Erin Richards, and Meg Jones

Milwaukee Journal Sentinel

Femelle, the most senior gorilla at the Milwaukee County Zoo, died this week, according to zoo officials.

A western lowland gorilla thought to be 54 years old, Femelle died Monday. She came to Milwaukee in 1985 from the National Zoo and gave birth to two offspring here, one male and one female, zoo officials said. Her offspring were sired by Obsus, the zoo's breeding male at the time.

The cause of her death is not known, though she did have cardiac disease, a condition that was closely monitored and treated by zookeepers for several years. Because of her age, she was considered to be a geriatric animal.

She was remembered as an excellent mother.

"At the time of her passing, Femelle had a strong relationship with our 2-year-old male gorilla, Sulaiman," zoo spokeswoman Jennifer Diliberti-Shea said in an email. "He adored her and they spent much time together. Her patience with him was incredible."

Gorillas live in family groups with one dominant male. In Milwaukee, that's Cassius. He led Femelle, half-brothers Maji and Hodar, and Shalia, the dominant female who gave birth to the youngest gorilla, Sulaiman, in November 2014, according to a Journal Sentinel story.

On social media, zoo officials said Femelle will be missed by keepers and visitors.

Video: Zoo gorillas bring 'Tarzan' rehearsal to life for Wauwatosa East students