Flying squirrels (Glaucomys), including the Southern and Northern species, are North America’s only nocturnal squirrels. They spend their nights gliding silently between trees, which often leads to the mistaken belief that they are silent creatures. These highly social animals communicate using a complex array of vocalizations often missed by human observers due to their nighttime activity. Their communication ranges from soft, audible chirps to high-pitched sounds inaudible to the human ear.
The Range of Audible Vocalizations
Flying squirrels produce a variety of sounds within the range of human hearing, though these are often soft and difficult to detect in the dark. One frequently described vocalization is the “trill,” a rapid, high-pitched series of notes. This sound is sometimes compared to the noise of a high-speed zipper or miniature machine gun fire because of its quickly repeated, sharp quality.
Another common sound is the “chirp,” which is shorter and softer than the trill. Southern flying squirrels (Glaucomys volans) also emit “barks” and “descending crows.” These audible calls are important for immediate communication, allowing individuals to quickly signal their presence or a potential danger across short distances. The variety of their calls, which also includes soft “mews” or “squeaks,” points to a nuanced system of social interaction.
Context and Purpose of Squirrel Calls
Audible sounds produced by flying squirrels are tied directly to specific behaviors and social contexts. Loud, rapid calls like the “trill” frequently function as alarm or distress signals when a squirrel perceives a direct threat. This vocalization alerts nearby group members to the presence of a predator, such as an owl, which may prompt a scattering or freezing response.
Softer vocalizations, such as muted “chirps” or “squeaks,” are used for social cohesion and communication among nest mates. These calls help individuals maintain contact while foraging or when returning to a communal nest cavity. Mating calls are seasonal vocalizations that are part of courtship rituals, though their specific acoustic characteristics can vary between individuals and species. The complexity of their communication system suggests they transfer information about social status, location, and environmental conditions.
Beyond Human Hearing: Ultrasonic Communication
Flying squirrel communication includes sounds above the limit of human hearing, known as ultrasonic vocalizations. Humans typically cannot hear sounds above 20 kilohertz (kHz), but flying squirrels produce calls reaching frequencies as high as 56.6 kHz. These high-frequency sounds are a common communication method among rodents, but their use in Glaucomys species has only recently been studied.
Flying squirrels emit several distinct types of ultrasonic calls, including broadband noise bursts and complex frequency-modulated vocalizations. One advantage of using ultrasonic frequencies is that the sounds attenuate, or fade, more quickly in the environment, making them difficult for certain predators, like predatory owls, to detect. This creates a private channel of communication for the squirrels, especially when they are regrouping at a nest cavity after a night of foraging. These specialized signals are likely used for close-range interactions, such as communication between a mother and her young, or for maintaining contact within their social nesting groups.