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| Earth on May 02, 2013

Flying squirrels reunited after 20 years with new road crossing

When biologists realized that flying squirrels were unable to cross over a stretch of highway, they devised a structure to help the squirrels glide across the road.

In 2008, biologists installed crossing structures to help endangered Carolina northern flying squirrels glide across a road. The road was blocking the ability of the squirrels to access mates, den sites and foraging grounds in the forests of North Carolina. Now, new research suggests that the road crossings are working—squirrels were observed using the crossing structures 14 times over the past few years. The research was published on February 28, 2013 in the Wildlife Society Bulletin.

Carolina northern flying squirrels are small nocturnal squirrels that are most active at night. While the squirrels cannot fly, they do glide through the air using the aerodynamic lift provided by a fold of their skin that stretches from their wrists to ankles. When gliding, the squirrels use their broad flat tails as a rudder to steer. Carolina northern flying squirrels are an endangered species that inhabit cool, moist forests in North Carolina, Tennessee and Virginia. Their populations are highly fragmented into only a few forest habitats.

In 2002, biologists noticed that Carolina northern flying squirrels were not crossing over a two-lane road located along a scenic stretch of highway in North Carolina’s Unicoi Mountains. Flying squirrels use tall trees to launch into a glide, and they typically can glide for about 5 to 25 meters (16 to 82 feet). The gap created by the road and the treeless area along the shoulder averaged about 38 meters (125 feet), which was too large for most squirrels to leap across. Not being able to cross the road was hindering the ability of the squirrels to access mates, den sites and foraging grounds in forest habitats throughout the region.

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Biologists Chris Kelly and Mike LaVoie tag a Carolina northern flying squirrel. Image Credit: Gary Peeples, US Fish and Wildlife.

Inspired by an Australian study that successfully used artificial structures to assist flying squirrels in navigating across road barriers, biologists from the North Carolina Wildlife Resources Commission and North Carolina State University installed three pairs of crossing poles along the road in North Carolina. The crossing poles were situated about 14 meters (46 feet) above the ground and they had a long horizontal platform attached to serve as a launching spot. Each crossing pole was spaced at distance of approximately 15 meters (49 feet) apart from another pole on the opposite side of the road. For 15 months in 2009 and 2010, the biologists monitored the road to see if the flying squirrels were using the platforms.

Findings from the study showed that squirrels were successfully using the new crossing structures. Squirrels were observed on camera leaping off the platforms 14 times during the study (you can view a video here), and radio-collared squirrels were found to be using habitat on opposite sides of the road from where they were first caught and tagged. The biologists are hoping that squirrels will continue to increase their use of the crossing structures over time.

Reconnecting the isolated populations of endangered northern flying squirrels may help to prevent this species from going extinct.

Authors of the study included Christine Kelly, Corinne Diggins and Andrew Lawrence.

Bottom line: Biologists from the North Carolina Wildlife Resources Commission and North Carolina State University installed crossing structures to assist endangered Carolina northern flying squirrels to navigate across a road barrier. They observed the squirrels successfully using the road crossings and they are hoping that the structures will help to improve the access of the squirrels to new mates, den sites and foraging grounds. Their research was published on February 28, 2013 in the Wildlife Society Bulletin.

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