Orc Breeds.

Perhaps the orcs originating from Mordor (those that Sauron didn't recruit from other parts of Middle Earth) would be better described as a tribe, although I beleive places like Mordor and the Misty Mountains would have been the home of many different orc tribes.
However,the Uruk-hai and the Trackers are definetly different breeds, having unique characteristics not seen in most orcs.
I think that in the case of Mordor and the mountains the particular circumstances of those regions have shaped different breeds. The mountain orcs were, for a long time free of Sauron and able to raid and pillage as they pleased.
The orcs originating from Mordor, which were a bit tougher than their mountain cousins (Grishnakh and the other Mordor orcs were able to keep pace with the Uruks) would have almost always been enslaved and had to worry about the Ring Wraiths and other such dangers of living in Sauron's home. This, in my opinion, would have made for a harder, more warlike life and thus a breed tougher than the orcs of the mountains.

I'll look this up but I think that the orcs were made for specific purposes. The example of trakers and uruk-hai is a good example.

also, orcs originated from mordor (Angband more accurately) as they were made by Sauron's master. I believe it says this in the Silmarilliuon but I'll check.
Bye for now
~celeborn

It is widely believed that Melkor bred the orcs in the pits of Utumno (early in the First Age) by corrupting elves that he had captured. These unfortunate creatures had their forms twisted into what we now recognise as orcs. Tolkien says this of orc tribes:
"and many indeed of the older tribes, such as those that still lingered in the North and in the Misty Mountains,"
-from Appendix F of LotR
This suggests that the orcs first made their homes to the north rather than in Mordor and this explains why the Mordor orcs would be a younger breed. Orcs probably didn't appear in Mordor until Sauron settled there in about SA 1000.
Sauron probably did breed the Uruks and Trackers for specific purposes, but I doubt that all breeds developed in this way. Perhaps Sauron was able to breed the orcs of Mordor to be tougher than the more typical orcs of the North, although I think it far more likely that he exposed them to hardships and relentless drilling by the Uruks to acheive this. Of course we'll never know for sure.

That makes sense, since Angband was in the north! (And so was Utumno.) Melkor's original orcs would most likely have been bred for the northern climate.

Tolkien specifically names only one "breed" of Orcs: the Uruks, which were bred in Mordor in the late Third Age and were used to colonize and control other areas, including the Misty Mountains.

Tolkien also mentions "smaller breeds" in chapter two of book six, and it's not unreasonable to assume that the Northerners described in chapter three of book three also fall into this category.
Beyond that though no other breeds are specifically named as such. However this doesn't mean that there weren't many other breeds of orcs in Middle Earth. The fact that there is more than one smaller breed of orcs supports this. Also, the way Grishnakh's Mordor orcs are described in book three chapter three certainly suggests that they are something different to the Northerners and the Uruks.