You wouldn’t know it, because these secretive, airborne mammals are strictly nocturnal, but where southern flying squirrels (SFS) are present, they are Ohio’s most numerous species of tree squirrel!
Left: A SFS pauses its scramble up the side of a chestnut oak. Right: A SFS awaits tagging.
Don Althoff, Professor Emeritus of Wildlife Conservation at University of Rio Grande and SFS extraordinaire, has been studying southern flying squirrels in southern Ohio for nearly 30 years, and the past two years, I’ve had the great pleasure of assisting in and photographing the process. I joined on six occasions, but other volunteers have as many as 40+ surveys under their belts!
So, if these elusive critters are so difficult to encounter, how does a survey work? It’s a little more hands on than taking a night-time stroll through the forested hills of an oak-hickory woodlot with a flashlight and crossed fingers. SFS are cavity nesters, but they don’t excavate their own cavities – they use what is available to them. In nature, that would be a dead, dying, or living tree with some kind of hole, or a cavity previously created by a different critter, such as a woodpecker. To that end, it may also be a nest box.
Althoff has crafted over 400 next boxes at 16 different sites in southeastern Ohio. The boxes bear a hole on one side measuring exactly 1.5 inches in diameter, and this is important – too large, and other species, such as red and gray squirrels, could make their way in and take over, something Althoff learned early on. Not to be outdone, however, the would-be squatters have been known to chew the edges of the entrance to fit their size, so adjustments were made. The entrance is now fitted with a metal plate to prevent any unwanted alterations. Occasionally, mouse nesting, bee hives, and even snakes are found, but largely, SFS are the inhabitants.
To avoid disturbing the squirrels during breeding and nesting season, Althoff runs the surveys in winter. Additionally, SFS nest communally in winter to share body heat, meaning the greatest number of occupants are found December-January – something his early monitoring revealed.
The crew heads out in the morning with the necessary gear – a ladder, which Althoff climbs to check the boxes for squirrel presence, nesting material, and the shells of gnawed open nuts – and a backpack containing processing equipment, including a scale for measuring weight, ear tags to provide unique identification for future box checks, small vials for scat samples, a large clear tube for transferring the squirrels from box to volunteers’ hands, and a tarp on top of which the whole process takes place.
Althoff stands below nest box no. 627.
The crew prepares the processing station while Althoff descends with a box.
Althoff checks a box; some days not a single squirrel is found, and other days double digits are found snuggled together inside one box!
Equipment is readied quickly, because it’s best to avoid handling the squirrels for too long.
Squirrels are not always found; some surveys produce no furry critters, but this doesn’t mean the study area is necessarily void of the research subjects. They may simply be choosing to nest in a natural cavity nearby instead. And still, even with no squirrels, important data is collected on whether nesting material and nut shells are found inside the boxes, and if so, how much. Althoff can even determine whether a nut has been chewed by a SFS or a different critter; the mouth of a SFS is small – too small to fit a nut all the way back in to be crushed by their molars, so it must be gnawed open to reach the meat inside. Their pointed bottom incisors also produce a telling beveled edge. If the shell in question has multiple holes, it was most likely chewed by a white-footed or deer mouse.
The data has shown SFS have a decided preference for hickory nuts above all else. It takes effort for the squirrels to cut through a shell, and because hickory nuts have one-and-half times more fat and calcium than acorns, as well as more sodium and phosphorous, they are the more nutrient-dense and energy-efficient choice. Additionally, hickory nuts have fewer tannins, which reduce the efficiency of the digestibility of the nut. Beech nuts seem to be a last resort, found rarely and mostly in years of poor hickory nut and acorn production.
After Althoff reaches a box, he plugs the entrance to ensure any possible occupants remain nestled inside. He then opens a door on the front of the box and peers through a screen behind to determine whether squirrels are present. If they are, he removes the box from the tree and brings it down to the tarp, already spread out by crew members and ready for action.
Left: The transfer tube is connected to the box. Right: A bewildered squirrel moves through the transfer tube.
The large, clear tube is fixed against the entrance hole on the box, and a crew member will encourage the inhabitants one at a time into and through the tube by either blowing into the box or with the assistance of an extendable backscratcher. The squirrel eventually makes its way to the end of the tube and into a state-of-the-art clear cake icing bag, held fast by another crew member. This allows the squirrel to be weighed, and then gently removed for sexing, tagging, possible collection of scat samples, and photographs for age determination later.
Thick gloves are necessary for handling; despite their sweet appearance, these tiny mammals can and do bite.
After processing, the squirrel is released onto the side of a large nearby tree, usually some kind of oak or hickory (beech bark is too smooth and difficult to climb, and shagbark hickory is too shaggy to traverse quickly), which it promptly scurries up. From there, usually three quarters up the tree or higher, it will jump and glide – because remember, despite their name, flying squirrels don’t fly with wings but instead glide with a flap of skin called a patagium between their limbs – to another tree and disappear.
Left: Ear-tagging allows Althoff to record whether any squirrels have been captured in a prior survey. One adult was captured a total of 5 times over a 6 year span. Right: Althoff takes a photograph in profile of every squirrel that is processed, with ear tag numbers and, if applicable, scat sample numbers typed into a calculator for easy referencing.
A recently released male squirrel with ear tag finds purchase before gliding to his next cavity.
Althoff’s research, as he writes in a 2001 report on his findings, aims to assess whether “the response (abundance and reproductivity) of southern flying squirrel populations to forest change (due to timber harvest, succession, and others) can be detected by yearly monitoring of nest boxes.” In short, the answer was yes – it was effort and cost effective to monitor the squirrels in this manner, especially compared to other research methods, such as radiotelemetry – and so monitoring has continued to take place every winter.
It’s a special and rare thing to view a southern flying squirrel up close, and an even more unique experience to handle one. Perhaps the most exciting and most anticipated moment of the surveying experience, however, is witnessing a glide. Watching them do what they’re built to do after a couple hours traversing steep, snowy hillsides with frozen fingers and a not-exactly-light ladder in tow is a rewarding, satisfying, and bright moment among the many gray and dreary days of winter in Ohio, met with excited cheers and content sighs.