The surgical markings are a type of rash that appears inside the national park.
The rash derives from contact with urushiol-X. If the rash is not treated, those parts are changed.
There is also an artifact sharpie which can draw them directly. Another of the “cylindrical quotidian” artifact line of everyday objects categorized by INNOCENT. As usual, those objects are related to an oily substance.
The thorn forest is full of nerve poison. This and many other national park irritants can act as a backroute for urushiol-X “real driving”. With enough exposure to urushiol-X your system starts endogenously producing it as a response to any negative stimuli; phantom rashes.
The national park can be navigated via desire paths. Upon appearing in the park, an initial “desire maze” or “game trail” is manifested from the combined neural circuitry of the trapped bipeds, usually from the anal-territorial circuit. Through time-binding, bipeds can create a “knot” in the maze to which they can return and sleep with minimal danger. If desire is 100% paths can even be manifested immediately, even through refrigerators and people. Without desire the national park contracts around intruders. This is why people with extreme overt or latent desire tend to survive the longest.