Frequent Flyer Program: observation sessions for Japanese Flying Squirrels

Yadoriki Water Source Forest やどりき水源林 is home for flying squirrels. They fly, or glide to be exact, from a tree to a tree, normally during night. To observe their activity clearly, afforested coniferous forests of 50 or more years’ old is the best. There, trees are planted geometrically, trunks are straight, and the plants don’t keep bushy boughs lower down. It is easy for humans to spot gliding squirrels between trees in dark. Two kinds of flying squirrels are dwelling in Yadoriki Forest. One is Japanese Giant Flying Squirrels (Petaurista leucogenys), and another is Japanese Dwarf Flying Squirrels (Pteromys momonga). Both use hollows in large trees for their nest, and avoid forest floors for their movement in order to protect themselves. The size of hollow is larger for Giant Flying Squirrels, whose entrance has at least about 7 or 8 cm in diameter, whereas “Dwarfs” can do with 5cm wide hole to enter. I’ve learned, except for nurturing pups, they use several hollows during their bouncing around in one night. I imagined, maybe, they slept in one of those their houses which happened to be their last during their busy traveling day in the forest … Real Frequent Flyers. To check if a hollow is used by flying squirrels, we study if the barks above and down the hole are splintered. The squirrels fly between the trees, but never intend to be a hole-in-one. They land on either upper or below the opening of their dwellings, and run down/up to the entrance. It makes the tree surface frayed. Ah-ha.

Could you figure out which tree has
 the scratch signs of flying squirrel?

The flying squirrels are diligent. Once they decide to have that nice looking hole for their new house, they remodel the place according to their preference. Is the size of entrance OK? If not, they nibble the hole to make their gate “just right.” They also adjust the space inside by gnawing and scrabbling. Then, the squirrels use something soft and dry, like finely shredded barks of cypresses, to make a large cushion, or cypress-scented carpet, covering the floor of their room. The animal actually cuts into fine threads by themselves the bark of coniferous trees to make their comfy bed. Theirs are ultimate beds naturally emit the vapor of cypress essential oil … As they use their home intensively, the edges of entrance wear off round nicely. Old cypress cushions are thrown away outside and new carpet is weaved by fresh and clean material. It’s important to look around those worn-off hollows and the floor in afforested coniferous forest. Could we find something fluffy lying on the ground of cedar and cypress forests?

This is an old rag for flying squirrel.

One veteran instructor told me a story of about 20 years ago. When the first idea of the Forest of Growing 成長の森 was floated for Yadoriki, several civil society organizations voiced their concern about deforestation of the area in order to create a space for planting. The current area for the Forest of Growing in Yadoriki Forest was known as habitat for Giant and Dwarf Flying Squirrels both of which need large enough trees. The opinion of the civil society produced a collaborative project between citizen scientists and those from academia, which was to identify the trees indispensable to preserve thriving communities of flying squirrels. Zones that had lots of such trees were kept as before, and comparatively less-used places were deforested and reforested by seedlings of deciduous trees with name plates of children who were financial backers for the water source forest. At that time, she continued, several trees were designated for nest boxes. I guess it was a sort of compensation by humans to flying squirrels after the disturbance of their habitat. Management of these flying squirrel houses is now done by Kanagawa Forest Instructor Association. During the observation sessions, together with natural hollows, instructors record the usage of nest boxes by animals. We also check if it is necessary to change the old boxes by new nests.

Yadoriki’s one of the Forests of Growing with deciduous trees,
 surrounded by the forest for the flying squirrels.

A preparation for new nest boxes

Early autumn, I joined an expedition of nest box changes for this year. Those were the boxes for Dwarf Flying Squirrels so that the houses were a size smaller compared with for Giants. We entered deep in Yadoriki Forest where no trekking road was available. Before starting the replacement, observing the old boxes quietly for a while was imperative. “You see? Man-made nest boxes are constructed by boards. They have definitely thinner walls than hollows of large trees. So, flying squirrels use them as a kind of temporary resting places before returning to their bed, especially during winter.” Hmmmmm, they are having a very reasonable life. It means it is possible for no one to use the box (which is very unlikely), or some other creatures utilized the man-made nest. My seniors told me not only flying squirrels but also bats and birds used the boxes for their housing. It is necessary to monitor who utilized the facility, and make adjustment if necessary. After recording the outer condition of the nest box, instructors set a ladder up against tall cedar trees and climbed up high to reach to the nest boxes. We then withdrew the old and installed a shiny new house at the same place.

Kanagawa Forest Instructors with ladder
 enter deep into the Yadoriki Water Source Forest …

On our way to the nest boxes,
 I met Japanese Freshwater Crab (Geothelphusa dehaani).
 The place was at least 100m higher than the Yadoriki River.
 Tough guy, this crab is.

Setting the ladder …

Going up …

Changing to a new nest box ...

Done!

This box was completely broken.

It is important to bring back the old box to the admin office of the Yadoriki Forest. There, we examined the old nest to see how it was used, and checked the “cushion” inside. If the contents were like egg shells or even a dead fledgling, the box was used not by a squirrel, but by birds. If it was for flying squirrels, as they normally throw away their poop outside the house, the carpet is clean. On the other hand, if the place was abandoned, or else, we could find feces mixed in the cushion that would tell the health of the owner of the place. It was surprising to see the droppings of Dwarf Flying Squirrel … they were “Dwarf,” half the size of a grain of rice. A veterinarian told me if we examined it in microscope, we could identify what the flying squirrel ate. The animals also scratched the walls of the man-made house in order to make the inside cozy. All showed flying squirrels were home-loving creatures. Inside of their tree house now, are they dreaming for warmer next spring to come?

Fluffy inside.

The bark was shredded to this level.

Those black somethings are poops of Dwarf Flying Squirrel.

Home remodeling by the squirrel.
 Could you see the entrance is adjusted?

Wow. The wall was modified this much.

A grown-up Giant Flying Squirrel can have about 50cm long body. + They would have another 50cm long tail. So, home for Giant Flying Squirrels must be large enough for the “Giant” squirrel to cozy up. It means (1) a hollow for them must be in a large and old tree, and (2) the tree is structurally vulnerable to outer shocks such as earthquake or strong storm. On the foot of Yadoriki Ohashi Bridge 寄大橋, there was an old cedar tree with 2 holes that lead to two-story hollows inside (so my senior instructors said). It was a very popular nesting place for generations of Giant Flying Squirrel. Then, two super typhoons came this September, and devastated the trees in the forest. Very sadly, a beloved nest for a family of flying squirrel was also broken in half. I’m sure those squirrels were victims of natural disaster. “Where are they now?” “Well, they must have moved to their other nests in the forest.” “If they have survived, that is.” “Yeah.” That place was loved by forest instructors too. The tree stood almost next to the parking space and it was easily observable from Hadano Forestry Road 秦野林道. The flying squirrels are active from dusk to dawn so that it was precious the observation spot we did not have to enter deep in the forest during the night. “That was disappointing.” “Where do we go this year to have annual fall observation session for flying squirrels?” “Well …” In the end, one November weekend night, we’ve been to another hollow and a nest box relatively easy to approach from the forestry road. We waited about half an hour each to see if any flying squirrel, bat, or anything, using the sites. We strained our eyes to see those round holes in 10m beyond, using torch lights covered by red cellophanes. (Those creatures don’t care infrared light.) Both of the entrance looked smoothed that meant somebody was using them. However, no one came.

Devastation

Oh my … no roof for the squirrels.

A new observation site …

We were waiting, waiting, waiting …

It was a bit disappointing, though I personally enjoyed sitting quietly beneath a tall cedar tree in a deep night forest. I felt like doing a meditation in chilly but calm air of a large forest, and had a little thought about Iwate 岩手, that legendary old woman who killed her daughter and a grandkid in a deep forest to fulfill an order from her employer (my post on October 26, this year). Why did Iwate could not enjoy such pure air in a quiet forest? She must have been obsessed to be a good servant too much … pathetic. Flying squirrels are common in Japanese forests, er well, bears and boars, monkeys, etc., too. If she opened her heart to the environment surrounding her, not always thinking flashy city life and her rich employer, she could have had a jolly company in the middle of a forest …

A dusk of Yadoriki Forest …

Eventually, the leader of the observation session concluded “Er, OK, at least tonight, no animal came to use these spots. Let’s return to the site where the destroyed cedar with a nest stood, just in case.” So, we visited the place once again. The fallen tree was cut from the bottom by the Prefecture, and its log was neatly laid on a slope. We searched any traces of squirrel both on the boughs of nearby trees and the ground. Then, the leader muttered in a hashed voice. “Look, there is something moving around on the ground.” We tried hard to see the movement of the animal and whispered each other in the pitch black forest. “Japanese badger (Meles anakuma)?” “Hold on … let me watch it more …” “… I don’t think so. It does not have a long nose typical of badgers …” “Its face is more round …” “It’s a Japanese raccoon dog (Nyctereutes procyonoides viverrinus)!” “… Yeah, the bridge of its nose has black fur. That’s a raccoon dog.” The forestry road and the floor where the raccoon dog moved around were separated by a steep cliff of about 5m high. “Clever one. It knows we cannot go down there. The animal judged the situation is safe.” It observed us several times without any sign of nervousness, and engaged in its task, probably searching for food, at its own pace. After parading in front of us for about 3 minutes, it went in the deeper forest where our infrared light cannot reach. That was a sweet encounter. Our leader proclaimed “Oh, we are so lucky! I really wanted to embrace and kiss that raccoon dog!” Now I hypothesize the place once stood a nice hollow for flying squirrels is a good place for the other animals to find food, or live a life of forest. Maybe, in a forest, there are such “nice spots” where many creatures gather naturally. We need to be open-hearted and patient to encounter such sweet places in a mountain … Poor Iwate. She could have had parties in a charming plaza of the forest with the living creatures who would never have ordered horrible things to an employee ...

Could you figure out a white flush in the middle of this photo?
 It’s an eye of the raccoon dog we encountered.

It was fun to search for flying squirrels in Yadoriki Water Source Forest, though I do not recommend you to try without any guide who knows the area well. If you fancy joining observation sessions of flying squirrels around Tokyo, please enquire Mt. Takao 高尾山. There, the curators of Takao Visitor Center organize night observation tours every early summer. (Info is here. RSVP.) Its route is almost all paved and public transportation is available very near to the observation spots. Some business people go there from downtown Tokyo after their work. As flying squirrels are commonly found in Japanese rural forests, when you plan an overnight camping in a Japanese forest of big trees, you could have a chance to encounter them. Look around for the clues I explained above. Good luck, and don’t be Iwate in a night forest.😉

A tail of Giant Flying Squirrel.
 I took this photo in Ashigara Fureai Village 足柄ふれあいの村,
 not in Yadoriki unfortunately.

If you find an environmental issues in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121 〒243－0121　厚木市七沢657

Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/