No one needs to ask why I study Siberian flying squirrels – just look at the picture! They have gigantic black eyes and soft, silvery-grey fur, and when you see them glide between trees, it’s magic. But there’s another reason: they’re mysterious, live at low densities and mostly nocturnal, and I enjoy a challenge. Though the squirrels have a huge range in forests of the boreal climate zone, from Finland east as far as the Japanese island of Hokkaido, they are declining in many places, including my study areas in Estonia. They are tiny, typically weighing half as much as a brown rat, but nevertheless need large expanses of mixed old-growth forest, with plenty of mature trees for nesting.
In fact, Siberian flying squirrels are tied to aspen. The colour of their fur matches aspen bark and the lichens that grow on it, while old aspens are favoured by great spotted woodpeckers, which excavate holes that are the perfect size for a female flying squirrel to raise a family. Indeed these old aspens are so important that each one is strictly protected. We’re also putting up nestboxes; in parts of Finland, almost half of the squirrels already use them.
Sadly there is a major problem: logging is fragmenting the forest. Flying squirrels are wary of crossing clearings or trails on the ground, so are split into small populations with only a handful of breeding females in each. They also become more vulnerable to the impact of storms and predation by pine martens and Ural owls. So we’re now working with foresters and logging companies to create corridors of habitat that join up surviving patches of old-growth forest. I’m quietly confident that we can give this endearing mammal a future as bright as its enormous eyes.