Where flying squirrels go to count sheep...

I tracked squirrels to find their nest cavities, which I then measured (eg. volume, the direction the opening faces, opening area). Flying squirrels are secondary cavity nesters, which means they use cavities excavated by another species, such as a woodpecker.

A regular cavity looks like the one on the right. If you're lucky, once you track a squirrel to its tree you can hit the tree with a stick and a squirrel will either stick its head out of the cavity or actually run out and up the tree. If you're REALLY lucky, you may even get a glide right out of the cavity to another tree. That's always fun to see :) If you look really closely, you can see the nose of a squirrel towards the bottom of the cavity circle.

But then sometimes northerns shrug convention and do this to me. It's not new news that flying squirrels build leaf nests. It was just a little unexpected given the cold winter temperatures. Southerns do not even build leaf nests this far north. So when I stumbled upon my first nest, I thought it would likely be an outlier. But then I found more and more leaf nests...

So that brings us to this winter. This winter I collected several known leaf nests from last winter and deployed them with temperature loggers to look at the difference between outside (ambient) temperature and temperature inside the nests.

So far analysis of that temperature information shows that leaf nests are likely equivalent to tree cavities for buffering capacity. Stay tuned for more rigorous comparisons soon.

Winter gear: Just mush

The field site where I measured cavity temperatures was at a research property owned by Trent University. It is an old farm property complete with mature sugar maple forest. There is a gate and dirt road in the summer, but in the winter this gets snowed in, so you have to walk into (and around) the property.

To set up temperature loggers in the cavities I outfitted them with microchip detectors (to detect any flying squirrels that went into the cavity) and used a "treetop peeper" (camera on an extension pole) to check the cavities for any other small creatures that could be using them. This was to make sure the cavities were empty when I recorded temperatures, so that I was getting the insulating effect of the wood, not any heating effects of animals sitting on my temperature logger.

The microchip detectors had to be attached to large batteries, and the treetop peeper was stored in a large waterproof case, so getting gear in and out of the site was no easy task. Instead of carrying it all, the PhD student had the brilliant idea of taking a snowmobile sled, loading it with the gear and attaching the tree lanyard as a harness. Now getting all the gear in and out was a breeze... unless the snow was wet and sticky, which in that case it was still pretty difficult to pull the sled. BUT once you broke a trail, it was smooth sailing all the way back out.

Not to mention my legs were in excellent shape by the end of the winter!