Whenever this creature attacks or blocks, if you control another non-Human creature, this creature gets +1/+1 until end of turn.
If you don't control another non-Human creature immediately after Wildwood Tracker attacks or blocks, its ability doesn't trigger at all. If you don't control one as the ability resolves, the ability does nothing. It doesn't matter whether you control a non-Human creature in between those times, or whether you still control one later in the turn.
