Vital Spirit
The Pokémon is full of vitality, and that prevents it from falling asleep.
Anger Point
The Pokémon is angered when it takes a critical hit, and that maxes its Attack stat.
It lives in groups in the treetops. If it loses sight of its group, it becomes infuriated by its loneliness.
It is extremely quick to anger. It could be docile one moment, then thrashing away the next instant.