Alaska Fish & Wildlife News
September 2004

Flying Squirrels:
Night Gliders are More Common than People Realize

By Riley Woodford
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Sitting in branches: A northern flying squirrel peers from a perch in a tree on Prince of Wales Island. These nocturnal gliders are widespread in Alaska and range from Ketchikan to Fairbanks.

With kitten-soft fur, a taste for fungus and a remarkable built-in paraglider, flying squirrels – the nocturnal cousins of the familiar red squirrel - are gliding through Alaska forests from Ketchikan to Fairbanks in greater numbers than previously suspected.

“Most people don’t even know they’re here,” said Winston Smith, a wildlife research biologist with the U.S. Forest Service. Smith has studied flying squirrels in Southeast Alaska since the late 1990s. “So far, data from Prince of Wales suggests that densities of flying squirrels are as high - or higher - than any that’s been reported in North America.”

“Flying squirrels are a lot more abundant than people realize,” said Jeff Nichols, a biologist with the Alaska Department of Fish and Game. Nichols live-trapped hundreds of flying squirrels as part of Smith’s research on Prince of Wales Island, and he’s trapped them in the Juneau area near Salmon Creek and Tee Harbor.

Population densities on Prince of Wales Island are two to four flying squirrels per hectare (2.4 acres). That’s comparable to average densities of red squirrels in many parts of Alaska - but red squirrels aren’t found on Prince of Wales. Both species are found on Mitkof Island near Petersburg, and Smith said red squirrels occur there at almost twice the density of flying squirrels.

Although the night-gliding rodents are somewhat less abundant than their noisy red cousins, they’re pretty widespread in the North Country. North America is home to two species of flying squirrel, the northern and southern variety. Smith said four subspecies of the northern flying squirrel live in Alaska and western Canada.

“They can be found in B.C. and up into the Interior of Alaska, and probably anywhere in the Yukon and Northwest Territories that it is forested,” Smith said. They have not been documented on Admiralty, Baranof and Chichagof Islands, although they are found on the mainland and many of the islands in southern Southeast.

The distribution of the four subspecies reflects how animals have colonized Alaska after the ice age. Before the last ice age, northern flying squirrels likely inhabited the continuous forested landscape that stretched across the continent. Then massive, continental glaciers fragmented North America into isolated realms and separated populations. Over time these groups became genetically distinct, distinct enough to be considered separate subspecies.

“There is good evidence that populations of flying squirrels in Southeast are more unique than we thought,” Smith said. “Flying squirrels in Southeast are very genetically distinct from other populations in North America. They are more similar to populations in the Appalachians than they are to populations in Oregon or Washington.”

The subspecies Yukonensis is the most widespread in Alaska and is found throughout the Interior. Zaphaeus is the subspecies most widespread in Southeast Alaska. Griseifrons is a subspecies found only on Prince of Wales and a few closely adjacent islands.

“Another unique subspecies, Alpinus, is found in B.C. and the Yukon and is also found in Juneau area,” Smith said. “It’s likely to have come down through the Taku River corridor and then moved north and south, but we don’t know how far.”

Smith said there are a lot of good reasons to study flying squirrels. One reason is that flying squirrels play an important role in the Tongass Land Management Plan.

To insure that viable wildlife populations can continue to exist in a place like Prince of Wales, which has been heavily logged and crisscrossed with roads, the Forest Service has set aside pockets of old growth forest as reserves. Three sizes - small, medium and large reserves – serve in different ways. Large reserves, important to bigger animals such as wolves, are fewer and farther apart, and smaller reserves are more numerous and closer together. But do they work?

“Northern Flying Squirrels are a model species, helping to test the validity of two basic assumptions of the conservation strategy of small old growth reserves,” Smith said. “The questions are: Are these large enough to support breeding populations, and are they close enough and connected enough that individuals can move between them?”

To address that, Smith and his colleagues have trapped, marked and recaptured hundreds of flying squirrels in a variety of different habitat types. They’ve put little transmitters on squirrels and studied their movements. They have looked at the population ecology of the animals. Students from the University of Alaska Fairbanks have documented the taxonomy, range and distribution of some of the different subspecies.

Smith said so far, the evidence from Prince of Wales Island suggests that small old growth reserves may be able to support breeding populations of northern flying squirrels.

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