Creature Feature: Humboldt’s Flying Squirrel

Elena Bilheimer, EcoNews Journalist

Humboldt Flying Squirrel. Photo by Dr. Nicholas Kerhoulas, Research Assistant and Lecturer, Department of Wildlife, Cal Poly Humboldt

Few rodents can capture the public’s attention and imagination like flying squirrels. Worldwide, there are about 46 species of flying squirrels out of the over 300 species of squirrels. Flying squirrels are found everywhere except Australia, New Zealand, Antarctica, South America and Africa. Papers published in 2017 documented the existence of a distinct species of squirrel — the Humboldt’s flying squirrel (Glaucomys oregonensis) — previously thought to be part of the Northern flying squirrel species (Glaucomys sabrinus). 

According to the 2017 paper by Arbogast et al. describing these new findings, this squirrel was named “…in honor of the eminent naturalist Alexander von Humboldt and in reference to the coastal northern California county that bears his name and lies in the heart of the geographic distribution of this newly described taxon (Fig. 5)”. The Humboldt’s Flying Squirrel was designated a unique and separate species due to genetic testing, and surprisingly, it was found that Northern Flying Squirrels and Southern Flying Squirrels (Glaucomys volans) are more genetically similar than Humboldt’s Flying Squirrels are to Northern Flying Squirrels.

This species is found on the west coast of North America from British Columbia, Canada, to southern California in the United States, which includes the states of Washington and Oregon. While this species of squirrel is not tied to a particular type of tree in a forest, they are forest obligate, and make their nests in the cavities found in trees, fallen logs, the ground, or even sometimes peoples’ attics. Barbara Clucas, a professor in the Department of Wildlife at Cal Poly Humboldt, conducted a study with the help of a group of undergraduate students that used baited camera traps to show that the Humboldt’s Flying Squirrel can be found in both old-growth and second-growth Coastal Redwood forests of the Humboldt region. However, they found that the number of detections and activity levels were greater in the old-growth forest, which may be because old-growth forests usually have more cavities available for making nests and dens.

While there is still a lot to learn about the exact tendencies and behaviors of the Humboldt’s Flying Squirrels, in general, female squirrels make their cavities warm and cozy by lining them with soft material and duff in order to provide a habitable environment for their pups. The reproductive activity of this species (breeding to lactation) occurs from April to August, with the females providing all the parental care.

One of the most charming and unique aspects of this animal is their diet, which consists mainly of truffles and other fungi found throughout a forest. Their foraging habits have also proven to be ecologically important, as they support young tree growth by increasing mycorrhizae (fungi that have a symbiotic relationship with the roots of many plants), and dispersing fungal species. Additionally, Clucas described squirrels as the peanut butter of the forest, as essentially anything would be delighted to snack on them. They provide an important nugget of protein for predators, especially for species of conservation concern, including both the Northern Spotted Owl (Strix occidentalis caurina) and Fishers (Pekania pennanti).

The flying squirrels’ penchant for fungi is one of the hypothesized reasons for their ability to “fly”, or more accurately, glide, in order to cover large distances in the forest and locate the random patches of their favorite food. Due to a large membrane called a patagium that stretches between their wrists and ankles, and another that goes between their ankles and tail, their anatomy essentially allows them to become a parachute floating between trees. This is a special sight, and actually catching a glimpse of  the Humboldt’s Flying Squirrel in action is rare due to their nocturnal and evasive behavior. 

Besides their uncommon method of locomotion, these squirrels also exhibit some other rare attributes and behavior. For reasons completely unknown to researchers so far, they glow pink under ultraviolet light, a discovery that was made while researchers were out surveying for insects with black lights and were surprised and confounded by the pink-purple animals gliding around them. In addition to their special ability to glow, flying squirrels tend to communicate through ultrasonic vocalizations, which are beyond human hearing range. The reasons behind this method of communication are also still unknown, but the hypothesis is that their predators can’t hear them when they communicate in this range. 

While there has been some research done on the Northern Flying Squirrel, there is still much to learn about the distinct Humboldt species. A lot of the data that has been collected thus far may have to be reapproached now that it has come to light in recent years that they are separate species with overlapping ranges.  Studying these creatures more closely and individually is made difficult by the fact that they are nocturnal and can be negatively affected by more invasive methods of research such as radio collaring and tracking rather than just baited camera traps. Through their research, Clucas and her team have found the baited camera traps and ultrasonic recorders to be useful noninvasive ways to learn more about the Humboldt’s Flying Squirrel’s habitat and have documented them in multiple places throughout Humboldt, including the Arcata Community Forest and Headwaters Forest Reserve. If you happen to be out at night in any of these areas, keep your eyes peeled for any flying creatures and try not to get too caught up in what they are saying about you out of your hearing range. 

Check out this video to see how flying squirrels use their pantagium to soar through the forest! 

For more information about the study conducted by Barbara Clucas and her team, check out her recent paper “Using Camera Traps to Survey Humboldt’s Flying Squirrels in Old- and Second-Growth Redwood Forests”, published in Northwestern Naturalist, or look into the 2017 paper by Arbogast et al. detailing the Humboldt’s Flying Squirrel as a separate species entitled “Genetic data reveal a cryptic species of New World flying squirrel: Glaucomys oregonensis” published in the Journal of Mammalogy.