This seems to be a situation that could go either way. In the case of either the DM or the Player establishing what ended the trail, we seem to have a unique case in Hunt and Track.
If the player is the one establishing what caused the trail to end, then this is the only move in the base game that allows a player to establish fictional circumstances that are not the results of the character's actions*. Normally, this would fall solidly into the GM base of: describe the immediate situation around the players at all times. Note that if the player is establishing what caused the trial to end, they are limited to "a significant change in its direction or mode of travel" by the 7-9 result.
If the GM is the one establishing what ended the trail, this is the only move that provides information that does not end with "The GM tells you what it is," or something similar.
Thinking Off Screen
This could just be personal experience, but I've found that generally when a ranger is using Hunt and Track it is in response (knowingly or not) to moves I have made while Thinking Offscreen Too, per the principle. Dan Bryant mentioned:
"I think the driving perspective behind my interpretation is that I
feel like the fiction doesn't actually exist until it has been
While this is definitely true and Play to Find out What Happens encourages us to allow for flexibility in the fiction based on what has been established, the world is NOT only what has actually been stated at the table. Instead, Think Offscreen Too instructs us to
Make your move elsewhere and show its effects when they come into the spotlight.
Allowing the Ranger to establish what ended the trail seems like it would come with the risk of taking away that opportunity.
Communion of Whispers
When you spend time in a place, making note of its resident spirits and calling on the spirits of the land, roll+Wis. You will be granted
a vision of significance to you, your allies, and the spirits around
✴ On a 10+ the vision will be clear and helpful to you.
✴ On a 7–9 the vision is unclear, its meaning murky.
✴ On a miss, the vision is upsetting, frightening, or traumatizing.
The GM will describe it. Take -1 forward.
This is another situation where it seems natural that the GM would establish the results of all three results, but is only specifically called on to do one of them. I'm not completely sure it supports one side or the other: The player narrating a clear vision could simply be filling in the blank spaces that GM's are required to leave by their principles, but a murky vision is much less easy to work into the fiction/facts of the game. Still, the move was similar enough that I felt it warranted inclusion.
Determine can be defined as both:
- to conclude or ascertain, as after reasoning, observation, etc.
- to decide upon.
Because of the unique situations, and the various definitions of Determine, I think playing it either way is probably fairly safe. I think how the move works is probably best left up to individual groups to decide. This can be done either in the situation or for the move as a whole. For my games, I will still lean on the GM establishing, but with "Ask Questions and Use Answers" as an option, as it seems more like to produce consistently positive results.
*The only move I've found remotely similar in effect would be the Bard's Unforgettable Face, which specifies that this previous interaction is absolutely "Your call." As well, this decision is in a trigger, rather than a result.