For something like this:
Only the cry of wolves, and the bleat of sheep[,] could be heard.
If the first comma weren't there, then I'm fairly certain the second would be unneeded; however given that the first comma is there, is the second needed then?
My guess is that it is needed because if there were no second comma, the two phrases would be separated and thus would be ungrammatical. However, I am not too sure since I see the comma omitted often (around the Internet, so obviously not a reliable source).