Board Thread:Custom Lore Development/@comment-26863727-20161003140924/@comment-26863727-20161004200326

Furthermore, it is specifically stated in The Silmarillion that even in the First Age they were "bred". Seeing as how Uruk-hai are a hybrid of Orcs and Men, it further cements the statement that there is some sort of reproduction going on, as only Eru has the power to bestow life, even if it is possible to manipulate existing life.

Here, I found the exact quote, which states that Orcs "had life and multiplied after the manner of the Children of Iluvátar", therefore suggesting sexual reproduction is possible. Also, Bolg is referred to specifically as Azog's son. Of course, there is also information that suggests that at least some of the time, they were created by being "bred from the heats and slime of the earth", which presumably would require a powerful sorcerer such as Morgoth or Sauron.

Of course, it is also possible that the various sources in the lore, having been written at different times in the history of Middle-Earth and likely by several different authors, are disagreeing on a debated topic, or simply using whatever the dominant theory at the time was. Elves didn't exactly stop to chat when they saw an Orc. Since Tolkien mentions that "in some places wicked Dwarves had even made alliances with them" in The Hobbit, it is unfortunate that these Dwarves didn't write down anything they might have gleaned about Orcish culture.

Since we have no sources that were actually written by an Orc or include an account from one, there's no surefire way of knowing how the species actually reproduced. For the reasons above, I believe that there are Orc women, which were originally female Elves, and that the women either stay together underground like the Dwarf women, or Morgoth ended up making them behave and look exactly like the men except in their genealogical function.