In NA and the colder areas, all snakes ball up for the winter. Garter snakes also do it. We have a pit beside one of the hydro poles in the yard at the gun range.
Every winter, it is full- about a 2 1/2foot diameter ball of garter snakes. I know for a fact, this has happened every winter in the same place, since 1979 - as with the video of the rattlers, the garter snakes are all sizes, all ages.