On March 4, 2021 the NHEC and Liberty Electric-NH were fixing the downed power line on Bear Island and other islands, and had small, open, four wheel style, single seat atv's with tracks for crossing the lake ice and island land so MAYBE that's what you see.
https://can-am.brp.com/off-road/us/e...k-systems.html ..... small one-seat machines with tracks? ..... there's another thread on this weather/wind storm, March 2nd or 3rd power down and they used small tracks to fix the power. Is very doubtful the tracked frozen ground could still show any tracks after six months of summer so who knows but BRP, Armand Bombardier, makes some hell-of-a-good very happening winter atv videos.