I'm no expert but I filled my tag last year. First, look at a lot of goats before you hunt. From there I learn to ID the larger more muscular bodies of mature goats, particularly Billies. If you watch a goat for more than 15 minutes you'll tell the sex when the lift their hind leg to scratch their nose. It's best to try and judge horn's when you know if you have a relatively large or small bodied animal. In the end 1" of length and a 1/2" of circumference may easily keep you from book, but to me a truely mature and big bodied, well furred Goat is the best attributes to look for.
I've been in that unit a few times, via Surveyor Ridge. Great country, lots of goats. There are some fires burning still in the Mallard Larkins, so check access before you go. Isabella Landing is still open as far as I know. Awesome country!
Jeremy,
Stating the obvious, but goat size can be tricky because there in nothing relative in the mountains to judge by except other goats. Also, a small bodied billy can have 9+ inch horns and a total stud can have a set of broomed 8.5" horns...so it can be about what you are looking for in a goat.
Once you've seen enough it is usually pretty obvious to tell if you are looking at a mature billy. They will have a long horse-like face and the ears will be small relative to the rest of the head features. Body size can be profoundly different. A three year old goat may look mature until he is next to a 5-6 year old goat. A mature goat will have a huge shoulder/chest and a comparitively small rear anatomy.
Once in awhile a nanny defies the norm and has billy-like horns and good body size. For quite some time the Idaho record goat was a nanny.
Look for the glands; look for that pronounced "hump" and dirty haunches of a billy. Once you compare a few in the field, you'll likely see the differences between a big guy and a younger goat. A mature goat will often show dominance over the smaller billlies too by poking them in the paunch, and butting them.
Good luck on your hunt, and be safe. Remember: Mountains are mental!
And as I read here before..."We goat hunters hunt up and beyond the sheep!"
Great advice thank you both! I pre scouted the area earlier this year, might of been to early or not enough time to see goats but it was still helpful. I'll check on that fire.