Wildwood Tracker
Creature — Elf Warrior
Whenever this creature attacks or blocks, if you control another non-Human creature, this creature gets +1/+1 until end of turn.
"This one was wearing shoes made of glass. She'll be no ordinary prey."
Titus Lunter
Throne of Eldraine (ELD)
• #183Rulings
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.
(wotc • 2019-10-04)
Rulings
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.
(wotc • 2019-10-04)