Oklahoma City Zoo officials were puzzled why Bridget, an 18-year-old lioness born in 1999, suddenly grew a mane which is a feature of male lions. Although the animal was not bothered by the head hair and did not faze Tia, her half-sister, and Hubert, a young male lion, the zoo's veterinarian, nevertheless, investigated.
Jennifer D'Agostino, the director of the zoo's veterinary services, believes it could have been caused by testosterone. She said there was likely an overproduction of the hormone that makes male lions develop manes when it reaches one year old.
Bridget is not the only lioness with a mane, The Washington Post reported. Five lionesses in Okavango Delta in Botswana also grew manes, confirmed Snopes.
Luke Hunter, a lion expert, opined that the sperm of the father of these lionesses was slightly aberrant which caused a disruption of the embryos. Another possible explanation is that the mothers of the lionesses had unusually high levels of the male sex hormone while they were pregnant. One consequence of the elevated testosterone levels is that these maned lionesses never become pregnant.
Hunter, a biologist and the chief conservation officer for Panthera, a global wild cat conservation organization, said despite being infertile, the lionesses are perfectly capable of survival.
However, Bridget's case is a little different because she grew the mane at an age beyond the middle age for a captive lion but not yet considered elderly. D'Agostino suggested it could be caused by a tumor perhaps in the animal's ovaries, adrenal glands, or pituitary gland.
To test her theory, it would involve comparing the testosterone level of Bridget with Tia which does not have a mane. Both animals are 18 years old. But it is a challenge getting a blood sample from a lioness, or a lion, for that matter. The zoo did not want to use an anesthesia on Bridget because of her age, so the zoo staff used operant conditioning, a standard training technique which rewarded the lioness with imported horsemeat from Canada every time Bridget laid down in a special crate.
It involved several crates until the zoo staff was able to use a hook to pull Bridget's tail through a little opening. They held her tail, pressed it with a blunt-tipped needle which was inserted into a vein to draw blood.
The results of the blood test showed normal levels. The zoo workers will try again this week to get another blood sample which they will subject this time to a hormone test. If Bridget's hormone levels would suggest a tumor, the staff will attempt to find its location and treat the tumor with hormone supplements to suppress the testosterone. If that will not work, they will perform surgery on the lioness as a last resort. But they will only do that if the medical team says it is necessary to improve Bridget's quality of life which a mane will really not affect it much.
Mane disappears after surgical removal of tumor in ovaries
In the case of Emma, a captive lioness at the National Zoological Garden of South Africa, tests in 2011 showed she had high levels of testosterone because of a problem in her ovaries. When they removed the problem, Emma returned to being a typical lioness minus the mane that she grew, New Scientist reported.
Given these cases, Hunter said it is likely there is a genetic component in the lioness population that underlies the phenomenon.
A two-year observational study of the five Botswana lionesses was published by the African Journal of Ecology in August 2016. The mane is used by male lions to attract lionesses. Geoffrey Gilfillan, a researcher at the University of Sussex who led the study, observed that one of the five, identified only as SaF05, also showed some male behaviors such as increased scent-making and roaring. She also mounted other females.
However, she did it less frequently. SaF05 frequently copulated, but she never got pregnant. It likely was SaF05 which was photographed by National Geographic photographer Deon De Villiers mating with a male lion in April 2016. The image became viral because people thought it was proof that homosexuality also exists in lions.
Hunter explained the aberration of the lionesses to the genetic contribution of the sperm or the problem goes back during the gestation when the fetus was exposed to increased levels of androgens, specifically male hormones such as testosterone.
He added that the masculine females likely occurred when the embryo was disrupted, either at conception or while in the womb. Hunter said that the manes may actually be a boon to the pride if the lioness is perceived as a male by other animals. She could better defend herself from hyenas or attacks by foreign male lions. But in the case of SaF05, she appeared to be treated a lioness by the rest of the pride.
[researchpaper 리서치페이퍼=Vittorio Hernandez 기자]