The various mane mutations in lionesses are all AMP, so a lioness with this mut wouldn't display her mane until she reaches two years old. There are cases of wild lionesses in Botswana that have grown manes - you can read about them here:

https://blog.nationalgeographic.org/2012/10/09/rare-maned-lionesses-explained/

https://www.conservatorscenter.org/2018/03/05/the-mystery-of-the-mane/

As you can see, these lionesses are often infertile but otherwise healthy and survive just well in a lion pride. It would be fun if these mutations had a gameplay effect that reflected these real-life maned lionesses. The mutation would trigger a high chance of infertility - say 50% - regardless of her mother's fert level. The infertility would be present from birth. You would still need to check her with the falcon's eye to see if she has an hidden AMP.

Do you like the idea of an in-game effect on the mane mutations? Let me know and give me some feedback on this idea.