My BCO had the same hissy attitude when I first got her Willow. She would huff and puff inside her tub and quiet down pretty quickly once I got her out. She's never tried to bite me though. I'd say it took her a month or two to completely calm down. She's as sweet as pie nowadays. Your buy Grimm is quite a handsome fella. I'm confident he'll mellow out after a few good meals.