Lab results have revealed the answer to a mystery at an Oklahoma zoo: Just what caused a female lion to sprout a mane. The Oklahoma City Zoo says in its March newsletter that testing at the University of Tennessee found the African lioness named 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 AP reports.
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. KFOR reports treatment isn't necessary right now, and that she'll keep the mane for as long as that remains the case. For male lions, testosterone production steps up around age 1, which is when they usually begin growing a mane. The zoo says female lions with manes are not unheard of, but they are rare. Indeed, National Geographic reports on a case from 2011 in which a 13-year-old lioness kept in a South African zoo similarly developed a mane; in her case, the mane was traced to a "virtually unheard of" issue with her ovaries. (A "lion whisperer" took three lions for a walk; it did not end well.)