Now, researchers at Cal Poly Humboldt are investigating the calls of these gliding mammals to gain new insights into their behavior and inform conservation efforts.
The northern and southern species of flying squirrel produce similar calls. So, when the Humboldt's flying squirrel was discovered to be a unique species, Wildlife Professor Barbara Clucas and a group of undergraduate Wildlife students including Travis Farwell set out to determine whether this newly classified species also used these high-frequency calls.
To explore this question, Clucas, Farwell and other students ventured into the dense coastal redwood forests of Humboldt, hiking through some of Humboldt’s most awe-inspiring landscapes to remote locations with specialized equipment to record these calls.
To capture these sounds, researchers used recorders initially designed for detecting bats, which rely on similar high-frequency calls for echolocation and communication. The method is minimally invasive, detects the squirrels’ calls, and helps distinguish them from other animals such as bats.
To analyze the recordings, the team utilized Sonobat, specialized software developed by bat biologist and Zoology Professor Joe Szewczak. Sonobat creates visuals of the frequency of recorded calls over time, allowing researchers to examine and categorize the vocal patterns.
Farwell was so intrigued by these unique vocalizations, he continued his studies as a graduate student with Clucas at Cal Poly Humboldt, exploring geographic differences and seasonal patterns of call types.
Though researchers are still uncovering the exact function of these calls, they speculate that the squirrels may use them to warn of predators, or for social interaction such as mating, foraging, or communication with offspring.
“Another aspect to consider is that most predators of flying squirrels (for example northern spotted owls) likely cannot hear these calls. By using vocalizations in the ultrasonic, they may be avoiding detection by predators,” says Clucas.
“We are also interested in investigating how differences in vocal repertoires across the three North American flying squirrel species (northern, southern, and Humboldt’s) might relate to evolutionary differences in the degree of sociality and influences of the environment,” she says.
With this research, which was published in peer-reviewed journal Ecology & Evolution, scientists are gaining a clearer picture of how the Humboldt's flying squirrel communicates and interacts in its environment.
Clucas and her team are now working with researchers across the country to create a computer program that will automate flying squirrel species identification from recordings, a project that will make surveying these nocturnal gliders more efficient.
By listening to what these nocturnal gliders have to say—however silently to human ears—scientists are gaining deeper insight into the complex and biodiverse world of the Pacific Northwest’s forests.