Pictured here the African lioness Bridget from the Oklahoma City Zoo has had zoo keepers baffled as to just what has caused her to sprout a mane. But lab results are in and Bridget has an elevated level of androstenedione, a hormone that can contribute to developing male features. Veterinarians compared Bridget's blood to samples from her sister, who has no mane. Bridget's blood also contained a higher level of cortisol, which regulates metabolism and the immune system.
The zoo says the results likely mean the 18-year-old lioness has a benign tumor in her adrenal gland that's producing the hormones, but that her health is excellent.