Zoo cracks the ‘Curious Case of Bridget the Lioness,’ who mysteriously grew a mane

The mane that Bridget the lioness mysteriously started growing in 2017 looked more like a scruffy beard compared to the wild blowouts sported by the kings of the jungle.

But, still, it struck the Oklahoma City Zoo and Bridget’s fans as quite odd. Given only males are supposed to grow manes, no one understood where Bridget’s was coming from. Bridget, an 18-year-old lion at the Oklahoma City Zoo, had lived a perfectly healthy life. She didn’t eat any unusual foods, sticking to the same strict diet all the other lions did. She didn’t take any unusual medications with a long list of side-effects either. But suddenly she had a beard, and the veterinarians were baffled. The zoo called it, “The Curious Case of Bridget’s Mane.”

On Tuesday, however, Dr. Jennifer D’Agostino, director of veterinary services at the zoo, broadcast a message in a video the zoo posted on its blog: “I’m here to tell you today that we think the curious case has been solved,” she said.

Blood tests held the key to the zoological mystery. First, veterinarians had to train Bridget to cooperate for blood tests that didn’t use anesthesia, as the Washington Post reported last month. The veterinarians prepared Bridget for drawing blood instead using what’s called operant conditioning: Each time Bridget allowed the vets to get one step closer to drawing blood from her tail, Bridget would be rewarded with a slice of horsemeat, imported from Canada. D’Agostino told the Post that, if they could compare Bridget’s blood samples and hormone levels with those of her lioness sister, Tia, that might lead to answers revealing the source of Bridget’s mane.

“She did fantastic, because she’s just so smart. She caught on really fast,” D’Agostino told the Post. “Once she had her meat, she had no problem.”

Finally, the results of the tests came in.

It turns out, despite veterinarians’ expectations, Bridget’s testosterone levels were perfectly normal, nearly identical to her sister Tia’s. The source of the mane, D’Agostino said Tuesday, stemmed instead from significantly elevated levels of two other hormones: cortisol and androstenedione.

Those hormones are both produced in the adrenal gland, while androstenedione is also produced in the reproductive gland. In both humans and lions, cortisol is responsible for regulating various functions such as metabolism and the immune system. Androstenedione is a precursor to sex hormones including testosterone, meaning it can be responsible for producing male traits – such as beards or, for lions, manes.

Bridget was making two-and-a-half times more cortisol than Tia and a seven times more androstenedione, the veterinarians found.

But, the next question was why?

D’Agostino said they believe that, since both hormones are produced by the adrenal gland, a small benign tumor may have developed on the gland, causing the erratic hormones.

Other than the fabulous lady-mane, though, D’Agostino said this has not caused any noticeable shifts in Bridget’s behavior or any health problems, which isn’t expected to change. They’ll continue to use the horsemeat treats to take Bridget’s blood several times a year to monitor her hormones and make sure she remains healthy, D’Agostino said.

“We do suspect she will continue to have her mini-mane. I don’t think it’s probably going to get much bigger than it is now,” D’Agostino said, “but most likely she will have that for the rest of her life. Otherwise, she’s going to have no changes whatsoever. She will continue to do her normal routine here at the zoo, and everyone will get to enjoy seeing our special lion.”