The easiest way to find the little ditch that they hang out in is to take the normal road through the plains, from camelot hills. Go past that station there and when you come to a guard tower (I think it's usually empty, it was when I was there), turn right. If you make the turn too soon, go a little further down. They're hard to miss.
I "studied" them for quite some time now and made an easy level 10 & 11 for my Ice Wiz just by "harvesting" them. Normally they are extremly ignorant (poor) animals that do not care about their population slaughtered around them. I used 3 ice spells on one and got 1 BB and 12 Silver (as level 11) in a quarter of an hour. Maybe you realize that some of them occasionally start running in one direction. This one is easy to kill in this "mode", maybe it needs to finish its "task" before reacting on attacks. But then (out of the sudden) the whole community gets somewhat angry and they come rushing in from all directions (just run to the tower if the 3 guards are there or to WD). There is no real danger. BUT ... I believe that some items your are wearing make them angry. I found the Ponder and wielded it (orange to me). After that they seem to have high aggro and even followed me up to WD (!!!). After I changed back to my Wiz Staff everything was fine again. Hope that helps for some of you.
Run South from West downs, you will see a guard tower where the road makes a sharp bend..there are lots of them on the hill just east across the road from this tower. Be carefull, they are neutral, but after we killed a bunch, their friends would join in.
Somewhere in west salisbary plains...I can't find them. I need to find them...Guard in West Downs gives out tasks to kill them. 18K xp for killing a yellow. Not bad if you ask me. Tasks rule.