I saw 4, and tamed 2 of these in the course of two days while loking for a pack leader. Maybe a 1 in 2 lair chance of finding one of these, not very difficult at all.
Tamed one of these on 03/24/04 on Chilastra about 3,000 meters West of the Science Outpost. Found 3 lairs close to each other, cleared them and came away with a Guardian and a Pack Leader.