The Sunspire why do piranha plant have bone in it?

The male had an odd tone. He didn't sound particularly threatening. If he wanted her off his mountain, this was definitely not the way to do it. Her tail swished of its own accord as she sized up the boy. He was the first younger boy she'd encountered since her brothers her left their mother several months before. She sniffed at him curiously, relaxing somewhat.

O-okay, Umi relented, blinking. She swallowed nervously, breathing deeply to compose herself. She straightened up after a moment, her goofy tail returning to a normal size. I'm Umi, I uhm, I came up here to watch the sun but clouds are in the way. Truth. She gestured with her nose at the valley below, now dipped in the golden shadow of cloud cover. Her gaze quickly returned to him, for though she was a trusting animal, she was not about to put herself in undue danger.