Flying Squirrels
High above the forest floor, southern flying squirrels launch from tree trunks, stretch their skin “wings,” and carve graceful arcs through the night air. Yet scientists still don’t know exactly how these tiny mammals steer, brake, or accelerate while gliding. Using Virginia Tech’s Cube—a spacious motion-capture theater equipped with wall-to-wall projectors and high-speed cameras—our team will film every millimeter of a squirrel’s glide in three dimensions. By tracking changes in body posture, orientation, and tail position, we will quantify the forces that keep the squirrels aloft and the maneuvers that let them thread safely through dense canopies. What we learn will reveal the limits of their aerial performance, explain how habitat fragmentation affects their movements, and provide new guidelines for forest management and wildlife corridors. The project blends biomechanics, ecology, engineering, and the creative arts to illuminate the hidden athleticism of one of Appalachia’s most charismatic night-time gliders.
Mid-term Report
Securing IACUC approval for live-animal work
We met with IACUC veterinarian Dr. Calvin Lau on multiple occasions to discuss best approaches for dealing with animal acquisition and potential housing. We also had a meeting with IACUC veterinary staff members Drs. Brooke Bollinger, Stephanie Trout, and Katie LaVallee.
The main takeaway of these discussions is that housing flying squirrels or sugar gliders requires heightened efforts compared to our typical lab animals (which are reptiles). Their status means that each facility that they are in, either for housing or experimentation, must be comply with USDA standards. Compliance is critical since these facilities can have unannounced inspections by the USDA twice per year. Therefore, the IACUC process for approval of such protocols is much more involved and time-consuming than a typical protocol.
However, if we were to work with pets with the permission of private owners, USDA approval is not required, depending on our exact experimental objectives. We are pursuing that line of action in regard to sugar gliders, which are an established but not common pet (Fig. 1).
Based on the advice of the IACUC veterinarians, seeking volunteers with sugar glider pets is our preferred approach while we continue our efforts of locating and identifying suitable flying squirrel populations in the wild (documented in section 2). We are aiming to submit the IACUC protocol as soon as we have finalized a best approach (aim: Feb 2026).
Locating and procuring animals for glide experiments
Efforts to locate pet sugar gliders
We have connected with one of two sugar glider dealers in the State of Virginia. The dealer (Ms. Amber May) is located in Floyd, VA. We have had positive communication with Ms. May about the potential availability of animals for experimentation in The Cube. However, exact details depend on the timing of the IACUC approval.
Efforts to locate suitable flying squirrel locations in the wild
To pursue experiments with wild flying squirrels, the first potential site that we checked is a cabin that is roughly 30 minutes north of Blacksburg. The owner of the cabin believed there was a large infestation of flying squirrels in the roof attic. We put 4 Bushnell Trophy Cam Trail Cameras (Fig. 2), borrowed from Dr. Ignacio Moore (Department of Biological Sciences), around the property and set them to record via motion trigger at night. After several weeks of trying different camera locations on the property, we could not find any evidence of flying squirrels. Several weeks later, the owner of the cabin (Fig. 3) informed us that he no longer heard the noises from the attic and found several large rat snake sheds nearby, so he believes there are no longer squirrels in the attic.
The second site that we checked was a collection of field sites on Fort Barfoot, a national guard base in Blackstone, VA (near Richmond). Mr. Brandon Martin is in charge of the box sites on the fort and is our contact that Dr. Mark Ford (Department of Fish and Wildlife Conservation) connected us with. Both have been very helpful with our project. The boxes (Fig. 4) were originally placed there for a fox squirrel study in 2019 but have not been used in several years.
During the fox squirrel study, flying squirrels inhabited some of the boxes, so we are hoping that some might be inhabiting the boxes.
In two trips to the fort by team member Josh Taylor, we checked 60/75 boxes using a small, custom-built, infrared camera on the end of a pole, which was placed inside the box. The first trip to Fort Barfoot was on November 3rd to check all boxes at sites A and C (Fig. 4; 15 boxes per site). In the second trip on November 14th, we were able to check all boxes at sites B and E. Unfortunately, we did not find flying squirrels in any of the boxes, although some had opossums, and all boxes had nesting material with some having green foliage, indicating more recent placement that might be evidence of flying squirrels. We still need to check site D, but it is unclear whether we should expect any flying squirrels at that site. It is possible that the temperature near Blackstone is still too warm to trigger the flying squirrels to seek seasonal shelter, so we will be checking site D one more time in January with the hope of finding some flying squirrels.
Development and testing of instrumentation IMU (inertial measurement unit) sensors
A key component of our question is to understand the movement dynamics of gliding animals in their natural habitat. To this end, we have been reaching out to sensor manufacturing companies in an attempt to find a bio-logging device that can be attached on flying squirrels without significantly impacting their movement capabilities. After exploring more than 30 sensor manufacturers, the most suitable seems to be a company called Druid. They make data collection sensors for animal research that range from less than 10 grams to more than 100 grams. Our requirement is for a bio-logging device that can record acceleration and GPS position of the animal, allowing us to extract the animal’s movement in The Cube and their natural habitat. The dimensions of the device need to be less than 25 mm x 75 mm with a thickness of less than 10 mm. The weight must not exceed 10% of the animal’s body weight (5 - 8 g), but would ideally weigh less than 5% of the animal's weight (2.5 - 4 g). The sensor must have a sampling rate of at least 100 hz for acceleration data and must be able to record the GPS position at least 10 times per day. The sensor must be capable of motion to trigger the data recording, as well as only recording during certain hours (after dark and before sunrise for nocturnal flying squirrels). The sensor must be water and dust resistant with a minimum IP (ingress protection) rating of 68. The sensor must have the battery and storage capacity to allow for at least 7 days of recording, followed by retrieval. The sensor must have a reliable method of locating for retrieval, either through radio signals or a proprietary system like Druid’s Intelink.
Two sensors, the Ultra C5 and C6, manufactured by Druid, generally satisfy these criteria and appear to be a good match. Their details are attached at the end of this report. We are currently in the process of determining which exact sensor is the best fit for our needs while being cost-effective. Prices range from ~$1k to $5k.
Sensor testing and calibration
To use an IMU sensor on a live animal, we also require a way of correlating on-body sensor data with real-world movement movement patterns. This correlation is required to be able to identify behaviors of interest (climbing, jumping, gliding) in the sensor data. Toward that aim, we have begun testing a large, inexpensive version of the IMU (Adafruit LSM6DS3TR-C 6-DoF Accel + Gyro). This IMU is not suitable for attachment on the animal, but it is useful for developing methods for correlating sensor data to movement data.
To test and calibrate an IMU for gliding experiments, we have developed a protocol to track falling objects and measure their position and orientation over time (Fig. 5). We utilize pairs of calibrated stereo-cameras to record the object falling (in this case a tumbling poster board) and extract both the position of the object (by tracking the center of the board), and the angular orientation of the board (by tracking the board corners). We can then compare the tracked data to data collected from the onboard IMU. This IMU uses an internal accelerometer, gyroscope, and magnetometer to collect data at 200 Hz and then computes the orientation using a sensor fusion algorithm (either a Kahlman filter or Madgwick filter). This orientation data can then be compared to ground truth falling object trajectories to compute the error and sensitivity of the sensor. Specifically, we aim to use ground truth data to compute sensor bias, nonlinearity, and noise.
