|Drey, or outside (as opposed to cavity), nests are often employed by flying squirrels during hot summer months. Sometimes
flying squirrels will make their own dreys, sometimes they will occupy
a vacant drey that was previously constructed by another tree squirrel
species such as the red squirrel (Tamiasciurus hudsonicus).
Dreys used by flying squirrels in North America vary in construction
materials and in size. Southern
flying squirrels will often employ fungal rhizomorphs, deciduous
leaves, bark and twigs in their
dreys, while northern flying squirrels often use shredded cedar bark
(among other barks), lichens, mosses, leaves and twigs in their dreys.
In the Pacific Northwest, the
northern flying squirrel employs the common Bryoria lichen as the main
constrution material for its drey nests.
There are one or two entrance/exit holes in a drey, and they are usually found on
the bottom, a location which keeps rainfall out. The drey is
constructed such that rough-hewn materials are woven on the outside,
with the material becoming finer in texture towards the middle. The
very centre consists of very finely shredded material.
Dreys are subject to the harshness of the environment and require
constant upkeep to remain water and predator-resistant. Some dreys have been
observed to be in use for over 10 years by generations of squirrels,
although the average drey may be used only one or two years before it
is abandoned and left to the elements.