Something interesting, not particularly known but interesting nonetheless, about people with Mutant-class Quirks, more specifically the Animal-subclass of Mutant-Quirks, is that the carriers of such Quirks inherit some of the instincts and habits of whatever animal or creature their Quirks grant them traits of. And sometimes the people close to the Mutant, usually the parents of a child who is the first holder of an Animal-classed Mutant-Quirk in the family, unfortunately don't know how to handle the extra needs brought forth by the Quirk. While the results of a family being unable to handle someone, usually children, with Animal-classed Mutant-Quirks varies, most cases weren't particularly extreme. Depending on the family, some of the worst things that could occur were murder, child abandonment and abuse.
An unfortunate case of a child who was the first in the family with an Animal-classed Mutant-Quirk being abandoned by their parents in the wild was the case of the young girl named Izuchi Midoriya, the holder of the Quirk known as Rathian. A Quirk that gave Izuchi the reptilian, or rather draconic, traits of the monster of the same name from the series of video games called Monster Hunter that was still ongoing, despite being very old, having started during the Pre-Quirk era. Much like the Flying Wyvern of the video games the name of the Quirk came from, Izuchi was fiercely protective of what she considered hers, but the other instincts that the Wyvern nicknamed The Queen of the Land in the games possessed often overwhelmed the young girl's young human mind, which caused a lot of problems for her and her parents. Namely Izuchi having a temper and easily becoming violent during her earlier childhood, something that the parallel scars on someone who could have become a friend of hers' face could attest to, Katsuki Bakugou (who nearly lost his left eye when a fight broke out between him and Izuchi over a toy (an All Might action figure to be specific, which ended up breaking in the middle of the resulting childish rumble (though no one's completely sure which one of the kids was responsible for breaking the toy))). Though considering just how violent some kids could get due to the animalistic instincts and impulses brought on by their Animal-class mutations, the fact that the worst Izuchi did was scratch and scar Katsuki's left cheek before resorting to merely wrestle with the boy, she was actually relatively tame, especially considering just how violent the creature the girl shared traits with were.
It was the mentioned incident of Izuchi scratching and scaring Katsuki's face that drove her mother, Inko Midoriya, who hadn't been able to truly understand her daughter and support her, over the edge. The fact that she had to raise Izuchi alone and work a lot to get by after her husband and Izuchi's father divorced her, claiming that she had cheated on him despite her claims that she hadn't, which was true (the same couldn't be said about Hisashi however), the stress of which from trying to make enough to not only pay the bills but also support herself and Izuchi chewing on her mind had probably something to do with her slippage of judgment and mental stability. While the green haired woman would come to later regret her decision, she drove away with Izuchi to a large forest well known for being the habitat for quite a lot of animals, named Endoru forest, and simply left her daughter there. Leaving Izuchi to fend for herself for years until the night where the holder of the Rathian-Quirk would meet the people that would become her new family.