They're a bit tedious to find - but there are a fair number when you know where to look.
1st - the gnoll gate from Antonica, as mentioned. They sometimes pop right in front of it.
2nd - North of the gnoll gate. I've seen them walking between the graveyard and the gate, sometimes two of them.
3rd - around the first pit, west from the gnoll gate. Never saw one on the second pit.
I killed scouts, everything at the towers, and the group on the hill.