Tee Pee structures from northern Michigan

I have 2 new interesting reports involving teepee-like structures. The first is of a structure discovered on a northern Mich two-track with an EC-like track beside it, and on the previous day there was no structure there. This may be the first time I have heard of a track near a structure.
The second case is a teepee structure shown to Igor and me by Chuck Lietzau in a southern Mich park (photos below). The park personnel told Chuck that it has been there with only a few changes for about 20 years. It is quite rare in my experience to have any information about how long teepee structures have been in place. The 2nd photo with Igor in the foreground and close to the camera gives the impression that the structure is only a little more than 6 feet high, but it is actually about 9 or 10 feet. There were some sticks about the size of broomhadles interweaved horizontally on a few parts of the structure.
As to what is the purpose of these type structures, I have no idea, but I have seen photos of several examples.
As opposed to just a few branches stacked up against a tree or interweaved in a free standing structure, these teepees would seem to require a lot of time and effort to gather up perhaps 100 sizeable tree limbs from the surrounding area and stack them in place. It is also noteworthy that these stacked limbs normally do not have side branches attached, or even the stubby remains of side branches.