Turn on the challenge first!
Equip an infinite poison arrow card to make this easier.
This achievement kind of explains itself, but it can seem like it is not progressing properly. Your progress will in fact update just fine. You cannot however, kill the wolves with an arrow. If the arrow kill the wolf and then the poison cloud disperses, you did not kill the wolf with poison. It's best to just shoo the ground in front of or next to the wolf. You will then need to skin the wolf to get progress.
WARNING: It seems the fully upgraded Dreamstinger Bow voids the achievement in some way. If you have issues with this achievement, use a different bow. Thanks to Burn The Dope for that information.