Prince of Wales flying squirrel

The Prince of Wales flying squirrel, Glaucomys sabrinus griseifrons, is a subspecies of the northern flying squirrel. Glaucomys sabrinus griseifrons is endemic to Prince of Wales Island in Alaska and has a unique coloration compared to other subspecies of northern flying squirrel. It is whiter on the ventral side, darker on the dorsal side, and the head/neck area tend to be more gray than other subspecies. This subspecies is genetically distinct from the northern flying squirrel from evidence found in mitochondrial DNA and microsatelite data.^[1] Adults are usually around 25-37 centimeters in length and 110-230 grams in weight. This subspecies is often considered a keystone species in the Southeastern Alaska area because it consumes and disperses conifer seeds and fungal spores into areas with little vegetation and sites of disturbance.^[2] The released fungi spores aid in the absorption of nutrients by plants and speed up regrowth in these areas.^[3]

Habitat and Range

The history of the range of griseifrons is unknown, but the subspecies probably colonized Prince of Wales after the last glacial maximum during the Holocene epoch.^[4] The Prince of Wales flying squirrel is found only on Prince of Wales Island now and a few neighboring islands in the Alexander Archipelago.^[5] Sitka Spruce (Picea sitchensis) and Western hemlock (Tsuga heterophylla) are the primary habitat for Glaucomys sabrinus griseifrons and they are associated with old growth forests.^[6] The population size is estimated to be greater than 10,000 individuals.^[7] Population densities are estimated to be around two to four flying squirrels per hectare (2.4 acres) on Prince of Wales.^[8] One study suggests that POW flying squirrel densities are among the highest recorded in North America compared to other flying squirrels and the subspecies can occupy a variety of forests.^[9]

Diet

Glaucomys sabrinus griseifrons have a generalized diet and can be considered carnivorous, frugivorous, granivorous, herbivorous and insectivorous. They primarily eat fungi, lichens, green vegetation, berries, seeds and insects. They have also been observed eating meat, young birds, and eggs. "Griseifrons" is suggested to be more generalized in its diet than other subspecies of northern flying squirrels.^[10] The American red squirrel tends to be the biggest competitor for resources for the northern flying squirrel. However, the American red squirrel is not found on POW islands therefore the POW flying squirrel does not have any major competitors.^[11]

Reproduction

The Prince of Wales flying squirrel is a k-selected species. They start breeding around one year old, or sometimes older, and usually have one litter each year of 1-6 young, averaging 2-4. Mating seasons tend to be around February through July, and the mothers will nurture them inside dens. The males do not play in a role in taking care of offspring. Infants take around five weeks after birth to become almost fully developed. After around ten weeks, they are able to glide and leap, and are ready to leave their mothers.^[12] The flying squirrel longevity can reach up to seven years old in the wild.^[13] From this, annual survival rates are suggested to be fairly high.^[14]

Behavior

Despite its name, flying squirrels do not actually fly. They glide using a flap of skin called a patagium. Since they are arboreal mammals, they spend most of their life in old growth temperate rain forests in the high canopy. They are a non-migrating species and typically stay near areas in which they were born. They are active all year, even in the winter, because they do not hibernate. During cold weather in the winter, they huddle together to conserve heat. Groups as large as ten individuals have been documented.^[15] They are nocturnal with greatest activity right before dawn and right after dusk. They rest in dens during inactive times. They have a strong olfactory sense that helps them to detect food.^[16] The POW flying squirrel tends to utilize dens in tree cavities or snags for storing food, hiding from predators, and reproduction.^[17] They do not spend much time on the ground in order to avoid predation. Northern flying squirrels are considered to be one of the most aerodynamic of mammals with the ability to travel between 3 and 45 meters in one glide. They travel between the trees to feed and in search of dens.^[18]

Predation and disease

This subspecies has not been found to have high predation rates. Predators of these flying squirrels include raccoons, martens, and probably barred owls. The raccoon population on POW is small, and therefore probably does not have a large impact on the flying squirrel population. Studies have shown that flying squirrels only make up about 5-7% of a marten's diet. A recent Prince of Wales inhabitant, the barred owl, likely predates on the flying squirrels, but there are no studies suggesting this. Humans have not been known to this hunt this subspecies because their small size leads to lack of meat and fur pelts. Disease has not been shown to be a limiting factor in population growth. Currently any disease that may be affecting these squirrels is unknown.^[19]

Management

Their primary habitat of old growth forests on Prince of Wales, for the most part, are not protected and timber harvests plan to remove 50-75% of old growth forests on the island.^[20] There is a push to protect the habitat of Glaucomys sabrinus griseifrons with not much luck. The Forest Service has dedicated a few areas of old growth forest reservations. Evidence suggests that small reserve areas of old growth forest might support breeding populations.^[21]

In 2011, an organization called WildEarth Guardians petitioned to have "griseifrons" protected under the Endangered Species Act. The United States Fish and Wildlife Service found that the petition did not include enough information to warrant the subspecies to be protected under the act. The USFWS listed several reasons for not listing the species under the ESA. A study found that the POW flying squirrel averages around 3-7 different dens per month which suggests that despite the forests of POW not being protected, the flying squirrels are not struggling to find suitable habitats.^[22] The USFWS also stated that another study shows population densities at 1-4 squirrels per hectare, suggesting that the subspecies is at a stable population level.^[23] Another study stated that gene flow and dispersal around the islands are occurring suggesting that these are not limiting factors for population growth. Other reports state that the population could decline between 10-30% in the short-term future due to increased timber and harvesting of forests on POW islands.^[24]

Future research must be done on several different topics. Research needs include clarifying taxonomic status, further sampling of range, determining population trends and abundance patterns, dependence on old-growth forests, and impacts of logging and harvesting to the viability of the population ^[25]

References