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OKLAHOMA CITY – Veterinarians at the Oklahoma City Zoo and Botanical Gardens say they have solved the mystery after an 18-year-old African lioness grew a small mane.

Last month, zoo officials said they were looking into why Bridget, the zoo’s 18-year-old African lioness, had suddenly spouted a mini-mane.

Male lions usually begin growing a mane when they are about 1-year-old, which is when they begin producing more testosterone.

However, it is extremely rare for a female lion to grow a mane.

Dr. Jennifer D’Agostino, the director of veterinary services at the zoo, announced that the medical mystery is solved.

Veterinarians took a blood sample from Bridget and her sister, Tia, to use as a side-by-side comparison to see what could be causing the mane growth.

They found that Bridget has elevated levels of two different hormones- cortisol and androstenedione. Androstenedione is actually a precursor to testosterone, which is the cause for mane growth in male lions.

D’Agostino says that Bridget may have a small benign tumor in her adrenal gland, which is leading to the increased hormones.

Veterinarians say they will continue to monitor her closely, but add that her condition is not likely going to affect Bridget’s quality of life. They add that she will keep her mini-mane as long as treatment isn’t necessary.