OKLAHOMA CITY - Bridget, the 18-year-old African lion known for her 'mini-mane' died Wednesday at the Oklahoma City Zoo and Botanical Garden. 

According to officials, Bridget died at approximately 6:30 p.m. 

Caretakers said they first noticed a significant change in Bridget behavior Tuesday morning. They said she was lethargic and uninterested in eating or training. 

During an exam, veterinarians discovered an excess amount of fluid building around Bridget's heart, which is an indication of heart failure or infection. Bridget endured a lot of pain, after the examination, officials said. 

The vet and caretaker teams made the decision to humanely euthanize Bridget, due to her advanced age and the severity of her condition. 

Zoo officials said the veterinary team will conduct and animal autopsy to determine her exact cause of death.