Whenever another Bear enters the battlefield under your control, choose one —
• Put two +1/+1 counters on target Bear.
• Target Bear you control fights target creature you don't control.
Either of Ayula’s modes can target any Bear you control, not just the Bear that entered the battlefield. Ayula can even be the target of its own ability.
For Ayula’s second mode, if either target isn’t a creature or is otherwise an illegal target as the ability resolves, no creature will deal or be dealt damage.