The tigermen were more obedient to their desires than regular humans. They ate when they wanted to eat, they slept when they wanted to sleep, and they killed when they wanted to kill. More than anything, they had extremely strong aspirations for survival. Tanner was no different. He wanted to survive, even if it meant betraying his home on Neotellus and siding with the Shadow King. His instincts told him it was the natural choice.