Scientists baffled after a lioness mysteriously sprouts mane

Veterinarians have been left baffled after a female lion suddenly sprouted a mane at an American zoo. Bridget, an 18-year-old African lioness living at Oklahoma City Zoo began to develop the usually-masculine trait in March last year.

The cause of the shaggy growth around the lion’s jaw is so far unexplained, although zoo staff said they were analysing blood samples in an attempt to solve the mystery.

“After a while, it became obvious to everybody that Bridget was developing something a little different,” Gretchen Cole, an associate veterinarian at the zoo told ABC News.

“Changes when a female develops characteristics of a male are unusual.

“It’s only the outward appearance of the mane that has changed. We are trying to solve the puzzle.”

Manes generally develop in male lions at around the age of one due to a heightened level of testosterone production.

While it is extremely rare for lionesses to develop manes, it is not unheard of and scientists have observed several cases in the wild in recent years.

In 2011, Emma, a 13-year-old lioness at the National Zoo in South Africa began growing a mane similar to that of an adolescent male.

Zoologists discovered the growth was related to a problem with her ovaries, which caused excessive testosterone production and the mane receded once the issue was resolved.

A group of five lionesses sporting manes were discovered in Botswana during 2014, as well as exhibiting typically male behaviour such as roaring.

Scientists believe that as the lions came from the same pride, the trait may have been passed on genetically and could even serve as an advantage by making it appear to competitors as if there are more males protecting the group.

Veterinary staff at the zoo say Bridget’s mane is unlikely to affect the quality of her life and that no other outward changes to her health or behaviour have been observed. 

They believe blood results could reveal the rare phenomenon has been caused by hormone imbalance.

However, the growth may have also been sparked by a benign tumour on the lioness’s adrenal or pituitary gland, causing irregularities in the way her body regulates testosterone.

Her sister, Tia, who is also 18 and living at Oklahoma City Zoo, has not developed a mane.

Rare Maned Lionesses Explained

Christine Dell’Amore, environment writer/editor for National Geographic News, wrote in National Geographic Blog (October 9, 2012), though uncommon, maned lionesses have been regularly sighted in the Mombo area of Botswana’s Okavango Delta, where the lion population may carry a genetic disposition toward the phenomenon, according to Luke Hunter, president of the big-cat conservation group Panthera, which collaborates with National Geographic’s Big Cats Initiative. (The Society owns National Geographic News.)

Hunter said it’s possible that maned lionesses in Mombo are related—including a safari favorite named Martina, which disappeared in 2002.

Such masculine females likely occur when the embryo is disrupted, either at conception or while in the womb, he said by email.

“If the former case, the genetic contribution of the sperm—which determines the sex of the fetus in most mammals—was probably aberrant, giving rise to a female with some male characteristics.

“Alternatively and perhaps more likely, the problem may have occurred during gestation if the fetus was exposed to increased levels of androgens— male hormones such as testosterone.”

If a lion mother had abnormally high androgens during pregnancy, her female offspring may end up “masculinized”—a situation that occurs occasionally in people but which is rarely observed in wild animals.

Whatever the case, such lionesses would likely be infertile but otherwise “perfectly capable” of surviving, Hunter noted.

In fact, their manes may actually be a boon to the pride—for instance, if the female is perceived as a male, she may better defend kills from hyenas or the pride from attacks by foreign males.

“It would be interesting to know if she behaved like a male,” he added. “Two similarly aberrant Serengeti lionesses were outwardly female—they did not have manes, but were almost male-sized, and they challenged and fought unfamiliar males for territories as though they were males!” (Independent & National Geographic)

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