A note of mine was published in the most recent copy of Northeastern Naturalist "Evidence of Multiple Annual Litters in Glaucomys sabrinus (Northern Flying Squirrel)" by Matthew J. Smith, Graham J. Forbes, and Matthew G. Betts
It has long been suspected that northern flying squirrels like southern flying squirrels and can have more than one litter a year. Determining the fecundity of flying squirrels is a challenge due to the difficulty of finding nest trees and climbing up trees to count the pups. Our paper was the first to show that flying squirrels can have another litter after successfully raising the first. One of our radio-collared squirrels (151.820 or "Petunia") had 5 pups in spring and another litter of 5 in the fall. Quite a handful!
Here is a link to the paper.
http://www.eaglehill.us/NENAonline/articles/NENA-18-3/21-Smith.shtml
We tried to use nest boxes as an easier way to attract female flying squirrels and count pups- but they seemed to prefer the natural cavities. From 100 nest boxes we only were found 3 active nests with young. The picture above shows one adult female looking out. She was protecting four pups.
This is a typical crack nest in a yellow birch. Very difficult to reach in. My arms were stretching while I stood on the last rung of the ladder. Not particularly safe.
Here are the pups from the above nest. They were 17g in weight, had closed eyes with short hair and thin tails. I estimated their age to be about 2.5 weeks.
