Lift off!
FLYING SQUIRRELS
In the forests of Hokkaido, Japan, lives a small, cute, furry mammal with a superpower: it’s the Ezo flying squirrel
“THERE IS A MOMENT when it will all come together.” That is what I kept telling myself. For months, I trudged through snow-covered terrain or stood motionless, neck craned, staring high into the trees. Many times I was defeated by their speed and stealth; many times I found myself questioning the decisions that had led me here. I was tempted to give up, but I was too stubborn. I refused to be beaten by a squirrel.
This prolonged contest of wills commenced quite by accident. In 2019, I was waiting for a fish. I spend the bulk of my time documenting marine life, and this requires planning. Capturing images of reproduction, for instance, necessitates being at a specific location at exactly the right time. Miss the moment and you miss the photo. You could say that I structure my life around the sex lives of fish.
But that year, the ocean was wonky. The animals that I wanted to photograph were nowhere to be seen. And thus I turned my attention to Pteromys volans orii, also known as the Ezo flying squirrel (momonga in Japanese), which is only found on Hokkaido, the northernmost of Japan’s main islands. It was actually my wife who directed my attention to this subject – she had wanted to see these charismatic creatures for years. They are not particularly rare, but their nocturnal tendencies mean they are not well photographed and that little is known about their behaviour. With nowhere else to focus my pent-up photographic energy, I was game.
So, we headed to Hokkaido, and I found myself standing under a tree during a howling blizzard, waiting. Nothing happened, except a dose of frostbite. But I was hooked. I would spend the next three winters on Hokkaido, getting to know its secretive squirrels.
“I would spend the next three winters on Hokkaido, getting to know its secretive squirrels”
The breeding season is an ideal time to study any animal. It’s a time when social activity increases, contests occur and dramas unfold. Ezo flying squirrels don’t hibernate, and they breed in both summer and winter. I chose the winter season for several reasons. Firstly, the squirrels develop fluffy, insulative coats against the cold, which makes them very photogenic. Secondly, there is minimal foliage on the trees, offering good visibility through the forest. Finally, there are no mosquitoes or ticks, and the island’s brown bears are safely asleep.
EZO FLYING SQUIRRELS ARE A subspecies of the Siberian flying squirrel (which occurs across the Eurasian continent between the Baltic Sea and Pacific Ocean) and live in the mixed conifer forests that blanket Hokkaido’s mountains. They live in holes in trees – both natural cavities and those excavated by other arboreal dwellers, such as woodpeckers – moving between abodes as and when it suits. Their diet comprises mostly leaves, buds, catkins, seeds and nuts, the menu varying according to location and season. Like other squirrels, they cache meals to see them through leaner times. I watched individuals plucking catkins from their hidey-holes many times, and even spotted one re-purposing an empty nest as a storage bin.
BUT PERHAPS THE MOST STRIKING aspect of these animals is their appearance. They are not particularly big – males average 17cm in length; females about 15cm, including the length of their tails, and are less than half the weight of an iPhone 13 – but they are incredibly charismatic, with large round eyes, a little pink nose, extended whiskers, rounded ears and a ‘smiling’ expression. They also have a way of holding their hands in front of them in a manner that oozes cuteness. They are real-life Pokemons; the very embodiment of Japanese kawaii (the culture of cuteness).
Naturally, these traits serve a purpose. Oversized eyes facilitate vision in the hours of low light, when the squirrels are most active; large ears act as an early warning system for predators. The contemplative hand position results from their ‘patagia’ – the wide, flat membranes that run along both sides of the animals’ bodies between their fore- and hind-limbs. And it’s the patagia that also gives these animals their most special ability: they can fly.
Technically speaking, squirrels don’t fly per se. Not in the self-propelled fashion of birds, butterflies or bees. They glide – but they do it extremely well and extremely fast, using their long tails as rudders and brakes. They travel in straight lines and gentle curves, but are also capable of mind-bending aeronautics. They can execute precision manoeuvres through dense woodland, weaving left, right, left and right again, and can throw in 180˚ U-turns. They can swerve and rollercoaster in the air and make enormous arcs around trees. As I commented to a friend, photographing a flying squirrel is like trying to photograph a tiny F-15 jet flown by a pilot on amphetamines.
My first few attempts to photograph an airborne squirrel were a complete flop. I was entirely unprepared for the wintery forest, I fumbled with my gear and I knew next to nothing about my subjects. (In my defence, these animals have had millions of years to evolve their speciality; I’ve had about 50. So it’s not really a fair contest).
Droppings are a sign that squirrels are nearby, though piles this large are unusual 
In a dispute over a female, an interloper is body-slammed off a tree by the defending male (right) 
An individual munches on a Sakhalin fir tree
“Photographing a flying squirrel is like trying to photograph a tiny F-15 jet flown by a pilot on amphetamines”
A SQUIRREL’S FLIGHT PATTERN – as I learnt in time – is complex. A lopsided U-shape, with the descent taking place along an angle of varying slope, down to the nadir, then upward to the landing point, which can be at just about any elevation. The speed, the angle of each segment and the acceleration and deceleration varies each time.
A study published in 2007 recorded both the horizontal distances and the associated vertical drops achieved during 31 squirrel glides. The longest distance was 49.4m; the greatest vertical drop 23.8m (or, as I prefer to think of it, two small blue whales across and one down). On average, the squirrels glided 18.9m distance and dropped 11.4m.
The measurements in that study reflect what I saw in the field. The squirrels are certainly capable of extended flight, but would usually glide from tree to tree, opting for extra distance only when necessary. There may be many reasons for this, but one stands out: risk management. Squirrels are vulnerable during flight, with raptor strike a persistent threat. One of my favourite squirrels – one of a pair that I had spent many days and nights observing – was taken by a goshawk.
I completed my second season in March 2020, just as the Covid-19 pandemic hit. I had been on Hokkaido for two months and had learnt a lot, yet my encounters with these elusive creatures had still been few and far between.
“Once, as I focused upon a pair perched directly ahead, the male looked at me, ‘grinned’ and peed”
MY THIRD SEASON, WHICH lasted for six weeks in the winter of 2021, was when my quest really took off. I devoted as much of my time as possible to hiking in the forest and chatting to locals. I still had so many questions. What are flying squirrels like personality wise? How do they interact with each other? Do they have friends? Enemies? Frenemies? I tried to think as much as possible like a soaring squirrel and how best to visually communicate the essence of what it is to be a mammal that defies gravity. I also had to figure out how to do that in the almost-dark.
As that season came to an end, I was beginning to understand flying squirrel behaviour. With luck, I managed to capture a few images. I also better understood what gear I needed – I’d been using heavy long lenses, which limited what I could achieve in terms of action shots.
It was my fourth and final winter of 2022 when chance and circumstance converged. A pair of Ural owls had cut the population of squirrels in the area by at least two-thirds. I was mourning the loss of my subjects when something strange happened. To quote Jeff Goldblum’s character in Jurassic Park, “life finds a way”.
Peek-a-boo: though usually nocturnal, the squirrels turned diurnal to avoid predation by Ural owls at night 
Ural owls are known locally as Ezo fukurou – ‘fukurou’ meaning ‘owl’ in Japanese 
A rare sight of a squirrel near the ground as it cautiously leans down to take some moisture from the snow
The surviving squirrels figured out that darkness now meant danger. Under pressure from predation, they switched to a diurnal schedule – giving me the opportunity to photograph them in broad daylight. The ample light, combined with three seasons of experience and now-appropriate kit, allowed me to capture the crucial aspects of squirrel life, from eating snow to hydrate to the body position adopted in the split second before landing. I captured them mating, fighting and feeding. I could plan and execute composite images to illustrate the speed and path of flight, not to mention the impressive quantity of poo the animals can drop in a single sitting.
I now knew my subjects well. I realised, for instance, that flying squirrels almost always urinate and defecate when they emerge from the nest. So, find the poo, find the animals. I also figured out that squirrels have distinct personalities and habits, and being able to identify individuals by behaviour alone was vital for anticipating what they would do next. Once, as I focused upon a pair perched directly overhead, the male looked at me, ‘grinned’ and peed. I yanked my tripod away just in time to avoid a direct hit.
It also became clear that the females are highly selective. Some males are welcomed into the nest while others are unceremoniously booted out. And when it comes to mating – well, let’s just say females sometimes exercise an option to get a little extra on the side. The moment when a cuckolded male catches on often leads to a dramatic encounter. There are looks of indignation, high-speed chases and shrieks of pain as the rivals battle it out in the branches. On one occasion, I saw a male body slam another in mid-air. The recipient of the blow plummeted to Earth but managed to open his patagia at the last second. He executed a steep upward arc, grabbed the tree and re-engaged his nemesis – all in less than the blink of an eye.
Interestingly, I saw considerably fewer skirmishes in my second winter and none in the third, which is almost certainly due to the declining numbers of squirrels. Yet owl predation comes and goes in cycles, and a reduction in prey means the birds will move on – they may have already done so. With time, the squirrel numbers will recover and the animals will revert to their nighttime habits. And the cycle will renew.
“There are looks of indignation, highspeed chases and shrieks of pain as the rivals battle it out in the branches”
IN TOTAL, I DEVOTED ABOUT SIX months of my life to these delightful animals in the wild, snowy forests of Hokkaido. The squirrels were very confiding, allowing me to walk among them – to watch, marvel, laugh and even mourn. It was magical, an experience I will always treasure. I hope I get the chance to visit my flying friends again one day. But for now, the ocean beckons; I must return to the water.
Frequent flyers
What other animals can take to the air?
THERE ARE MANY ANIMALS that can take to the air to one degree or another.
In Japan, there are two other flying squirrel species – the Japanese dwarf squirrel (Pteromys momonga) and giant flying squirrel (Petaurista leucogenys), though neither live on Hokkaido. Several dozen more flying squirrel species are distributed throughout Asia, North America and Europe.
The world’s smallest gliding mammal is a marsupial, the feathertail glider (Acrobates pygmaeus) found along the eastern seaboard of Australia and over to South Australia. It measures up to 8cm in length, tipping the scales at 12g.
Also found in Australia are the southern greater glider (Petauroides volans), a large marsupial that can be up to 60cm in length and weigh 1.7kg, and sugar gliders (Petaurus breviceps), which are possums with a penchant for nectar and sap.
Other gliding mammals include the colugo, aka the Philippine flying lemur (Cynocephalus volans), and the Sunda flying lemur (Galeopterus variegatus), whose native range is from southern Myanmar, Thailand, Vietnam, Malaysia and Singapore to Indonesia. Though both animals are called flying lemurs, neither is in fact a lemur. The name possibly derives from a passing facial resemblance to lemurs, which are found only in Madagascar.
An ability to take to the air isn’t limited to warm-blooded animals though. There are hundreds of species of flying frog, for instance. One well-known example is Wallace’s flying frog (Rhacophorus nigropalmatus), found in trees in Thailand and Peninsular Malaysia, as well as on Sumatra and Borneo. These amphibians glide using membranes between their limbs. There are also flying geckos, lizards and snakes, and tropical spiders and ants in at least five genera are known to glide.
Even some marine animals can take to the air, presumably to flee predators. These include dozens of species of flying fishes, halfbeaks and squids.
THE TECHY STUFF
Caught speeding
To quantify the speed of squirrels in flight, I positioned my camera frame to encompass 2.5m. After multiple attempts, I captured a squirrel travelling through that pre-determined zone, recording eight frames while shooting at 30 frames per second, which equates to 33.7kph. My distance measurement was not exact, so I settled upon a working estimate of 30- 35kph. Knowing this underscored the fact that relying on reaction speed is a fool’s errand: my brain is too slow. The only way to get the photos I wanted was to anticipate behaviour and be prepared.
ABOUT THE AUTHOR
Tony is a photographer from Japan who usually specialises in marine wildlife and is a winner in this year’s Wildlife Photographer of the Year. See more of his work at tony-wu.com.