Tuesday, August 18, 2015

Flying Squirrel Meet-up

Northern flying squirrel (c) John Ashley
Met a flying squirrel late last night while helping Glacier Park biologists capture/measure/release native bats. He vaulted silently from a tree somewhere in the midnight dark and made a surprise landing in one of our mist nets. We were pleased to make his acquaintance; he felt otherwise. He immediately anchored his teeth on one gloved finger while three of us untangled him by the dim light of our headlamps. He didn't want to let go even after we freed him from the net, clinging to an empty glove that was way too big to fit his tiny hands. He eventually relinquished the prize, and we place him on a nearby cottonwood trunk. He shimmied up and disappeared back into a nighttime ecosystem that our eyes can only wonder about.

Northern flying squirrel (c) John AshleyOur northern flying squirrel (Glaucomys sabrinus) is built to work the night shift. Our daytime red squirrel (Tamiasciurus hudsonicus) returns to its nest before dusk because it can't see in dim light. But even though the flying squirrel is considerably smaller than its daytime cousin, its eyes are twice as large to gather more light at night. While red squirrel eyes have mostly color-detecting cone cells, flying squirrel eyes have mostly dim light-detecting rod cells.

Like other nocturnal animals, flying squirrels also have "mirror" behind their retinas that reflects dim light back to the rod cells, effectively amplifying their night vision. This tapetum layaccounts for some of the animal eyes that you and I see when we shine a flashlight into the dark -- our light reflects off the animal's tapetum bright enough for our eyes to see.