The development of manes is governed by hormones, particularly testosterone, and is influenced by age, climate and genetic selection. They are sexual ornaments that signify masculinity and status, and are seen only in males - usually.
There do appear to have been a couple of credible cases of maned lionesses in Philadelphia and San Antonio Zoos in the USA, resulting from hormonal imbalances in middle age.
- 10 animals that can kill a lion
- It is one of the most iconic, revered – and feared -mammals in the world – with a powerful roar that can be heard for miles
There have also been reports - years apart - of two maned lionesses in Botswana's Okavango Delta. I am not aware of DNA analysis confirming the precise balance of their sexual identity, but I assume each had a genetic defect. I also suspect that the elder one would have been infertile, so the condition was not inherited by the other.
- Why do lions take so many sexual partners?
- Incredible survival story: Meet the three-legged lioness who defied death after getting caught in a poacher's snare 8 years ago
The two cases could represent a sign of inbreeding within the wider Okavango community, which causes all sorts of genetic anomalies. The condition could be more common than we imagine. When we see a mane, we assume we see a male, so rarely investigate further.
In 2016 it was also reported that five wild lionesses in Botswana grew a mane and started acting like males.
Too little is known to speculate on how a maned lioness would be treated by her peers. The one in Philadelphia zoo seemed to have a normal sex life, and those in the Okavango don't appear to have been ostracised.