How do Red Squirrels (Pine Squirrels to those of us who have migrated West from Wisconsin), not sink in deep, fresh snows? They actually excavate and use tunnels throughout the winter! (Grey Squirrels do not.) Their own private Metro good for not only navigating in deep snow, but for escaping dogs.
Here's one of their favorite tunnels - you can see all the traffic it gets. Think Chicago's Union Station.
The quarter is there for a scale/size comparison. This Metro runs from under a Norwegian Spruce, down our sloping garden, exits into the driveway (where apparently they pick up a transfer) and then back into the Metro, up the sloping garden on the other side of the driveway direct to... yes, you guessed it: our front yard birdfeeders!
This is what the tunnel looks like from above:
What do they do when they come to a tree? Easy!
Once the tunnels are in place, they're of course used by other tiny critters, namely voles and mice. I've seen them scampering in and out of them in order to get to their own unique tunnels that are just under the snow's surface.
Now if only I could get a photo of the squirrel popping its head out of the tunnel... I never seem to have a camera with me when they're scampering through their Metro.