Secret Squirrel

The Siberian flying squirrel (Pteromys volans) is one of Europe’s rarest and most endangered mammals, and is declining across its range in Finland, Latvia and Russia, as well as in Estonia. Photographer Nick Upton has spent some very long days (and nights) in the field capturing some rare images of this unusual and engaging creature in an Estonian forest.

Widespread in Estonia less than 20 years ago, it is now found only in Viruuma county, with little over 100 records in the last 10 years. Biologist Uudo Timm, of the Estonian Environment Agency, is fighting hard to help reverse this trend, as Nick Upton found out.



The Need For Mature Forests

Siberian flying squirrels (Pteromys volans) live in mature forests with a mixture of old aspen and birch among the fir trees. Only small pockets of suitable habitat remain in Estonia, and even these are surrounded by clear-felled areas and younger monocultures of firs, which can’t support squirrel populations.

Old forests are vital for the squirrels’ survival as they provide both food and habitat. Aspen and birch catkins are important spring foods for the squirrels, and old deciduous Aspens with rotten, hollow cores (created by Aspen polypore fungus) are important as nesting sites.

The Search for Squirrel Scat

Photographing these shy creatures posed several challenges as Nick explains, ‘the squirrels tend to emerge from their nests at night to feed, gliding from tree to tree on flaps of skin stretched between their legs. They do sometimes emerge briefly during the day, to relieve themselves, giving patient photographers a brief chance to photograph them in the daylight.’

One of the signs a tree is inhabited by squirrels is a pile of distinctive droppings at the base of the tree. Biologist Uudo Timm, who has been studying the flying squirrel for over 30 years, searches for these piles to record their presence.

More Valuable than Gold…

To Uudo, these droppings are more valuable than gold, as he can use them as evidence to gain a preservation order on the surrounding forest, barring tree-felling within 25 metres of occupied trees. On one occasion, he found flying squirrel droppings in privately owned woodland and it led to the landowner being prevented from felling an estimated €1 million worth of timber! Fortunately, some foresters favour sustainable piecemeal harvesting of woodland, and see benefits in owning more diverse forests, where ecotourism such as bear-watching now offers them a new income stream. But others refer to the flying squirrel as the ‘grey rat’ and resent Uudo’s work recording them, as it prevents them from clear felling forests.

Without protection, large swathes of forest can be clear felled. Not far from one of Uudo’s study sites, felling is evident. Piles of old aspen can be seen beside a forest track, with hollow cavities ideal for squirrels to make their homes.

To provide more nest sites for flying squirrels, Uudo installs nest boxes – with help from local forester Toomas Rennel. The squirrels prefer nest holes they can only just squeeze into, as this prevents pine martens, a major predator, also gaining entry. For the same reason, they prefer thick wood that isn’t easily chewed through, but the ideal home is an old tree.

Uudo uses trail cameras to record squirrels coming and going from his nest boxes and natural tree holes. He also sets a unique kind of trap to catch hole-nesting squirrels as they emerge at night, and is thrilled when he catches one, knowing how much he can learn from it. Once it’s out of the trap, Uudo holds the squirrel, while field assistant Kylle Kiristaja deftly attaches a radio collar. Uudo’s team can then radio track the squirrels to find out more about how territorial females and wider ranging males use the forest.

Thanks to Uudo’s work, much more is now known about the flying squirrel, and how crucial old forests are to their survival. Uudo now also campaigns for corridors of forest with trees at least 15 metres tall to be left between surviving fragments of forest to facilitate squirrel movement, and also for a wide age range of aspen and birch to be allowed to develop in woodland to aid with the dispersal of young squirrels. A major new EU LIFE project is now funding further work on, and forest conservation for, flying squirrels in Estonia and Finland. This remarkable animal remains highly endangered, but much valuable effort is going into learning more about it and how to protect it.


Siberian flying squirrel in flight {Pteromys volans} Finland


Portrait of wildlife photographer and filmmaker Nick Upton

Nick Upton has been fascinated by nature of all kinds since he was very young and began photographing it as a teenager. He trained as a biologist and then worked at Oxford University before making many wildlife films for the BBC, other major broadcasters and the RSPB, and has concentrated on shooting wildlife stills and video clips in recent years. He photographs a wide variety of subjects and specialises in documenting wildlife conservation (such as mammal, amphibian, eel and swift conservation and the reintroduction of cranes and beavers to the UK), combining shots of wildlife and animal/people interactions.

Click here to see a full gallery of Nick’s work.