Like most other Raptor-type mobs found in the game, these use a breath attack that causes Disease. If you're not tanking, try not to stand in front of them if you can help it (can be quite difficult, especially with lag, etc.) so you can avoid it. Otherwise, make sure you have a Viruna handy or you'll be unable to rest HP/MP back.
I've also seen them use Ripper Fang and Chomp Rush, like all other Raptors. If they have an ability that is unique to Aht Urghan/Besieged, I've yet to see it.