The northern flying squirrel lives in every province in Canada, but this nocturnal creature is rarely seen – or heard. During the day, flying squirrels stay hidden away in their nests in tree cavities, but when night falls, they emerge to glide silently between the branches.
Or at least they seem silent to us. Northern flying squirrels communicate via ultrasonic calls that are so high-pitched they are not audible to the human ear.
Trent University’s Sasha Newar is cataloguing those sounds. In collaboration with the Toronto Zoo, the Ph.D. candidate spent six months recording the high frequency calls in over 40 species of mammals. The result will be the largest sampling of ultrasound in non-echolocating mammals in the literature -- a detailed library of flying squirrel sounds.
Research into ultrasonic calls could enable better documentation of elusive flying squirrels
“Flying squirrels are difficult to trap, but by using microphones, we can sample large areas and detect numerous species without human interference,” says Ms. Newar. “The problem is we don’t know enough about the calls being made to apply these bioacoustic monitoring techniques. This research will help detect flying squirrels and build base knowledge to use this technique for other species.”
The sounds that microphones pick up are recorded on a spectrograph – a graph that visually represents audio frequencies, much like the audio recording app on a mobile phone. Ms. Newar is exploring whether different flying squirrel species have different ultrasonic calls, which will enable researchers to identify which flying squirrel species are present by the signature of their calls, without having to catch the squirrels.
The opportunity to contribute to long-term species monitoring is part of what drew Ms. Newar to Trent.
“My supervisor Jeff Bowman is one of the only long-term flying squirrel researchers in Canada,” Ms. Newar says. “I worked for Jeff for four months before starting my graduate degree and had the opportunity to work on bats a handful of times. I thought the ultrasound calls they use were really interesting and were understudied in other animals. Sure enough, flying squirrels use ultrasonic calls too.”
Flying squirrels’ fluorescent fur is outside the range of colour that humans can perceive
It isn’t only the sounds they make that are imperceptible to us. Flying squirrels also have traits that are not visible to the naked eye. When exposed to ultraviolet light, the fur of flying squirrels’ fur is fluorescent pink and fluorescent blue.
We are not yet sure why this is, but Trent undergraduate student Bryan Hughes is using mass spectrometry to examine what organic molecules are present in the pink fur, in the hopes of determining what its purpose is.
Mass spectrometry identifies the presence of organic compounds by precisely measuring the mass of charged ions. Different molecules have a slightly different mass, so with a precise enough measurement, it’s possible to identify which organic compounds are present.
“Determining the potentially fluorescent compounds within flying squirrel fur is an important piece in understanding why these animals are fluorescent," says Mr. Hughes. “Once we know what causes fluorescence, we hope to evaluate its ecological significance. It is also possible that it has no ecological significance. It could be a trait that was present in an early ancestor which was simply retained by the flying squirrels.”