I agree with mwestwood. The men are the true interlopers. They have brought their blood feud into the wild beauty of nature, and while nature would expect the beast to be cruel, humankind is not meant to act like animals. As retribution, nature ensured that each man got his wish for "the other's death."

Since you have put Interlopers as the title, the question seems to imply interpretation of the story per se. One interpretation can be that the men, both Georg Znaeym and Ulrich von Gradwitz are interlopers, or trespassers into the pristine state of the forest.  Nature shows its disapproval of this violation with two punishments:  the fallen branches and the wolves.

The word interlopers is what probably has three meanings.  The word itself means intruders, so let's look at three kinds of interlopers in this short story.  First, one of the men was an interloperon the land--it belonged to one of them, and so at least one of them was trespassing.  Second, How about the idea that the men were not where they should have been on that stormy night.  It says even the night animals were running for shelter in the storm; none of them were out in it.  Finally, of course, the wolves are interlopers in this new pact of friendship.  They just don't belong.

The Interlopers is not one of those stories that is up for many different interpretations. While it does have a surprise ending, the "rescuers" are actually wolves, the ending is not really ambiguous. I suppose one might be able to predict what happened to Georg and Ulrich, perhaps one of their parties arrived just in the nick of time. Maybe the wolves nudged one of the men free and they got a chance to become friends. Maybe the story was written as an allegory for how World War I started (see the link below).