Squirrels
are small. One of my senior Forest Instructors is a registered hunter for
Kanagawa Hunting Club. He said under Japanese jurisdiction standard gun for
hunting is shotguns. Hunters then choose bullets according to a game. The
smallest 410A is inevitably for the smallest animals. “These days, it’s made of
iron, not lead, in order to avoid any possibility of poisoning after use.” “Wow,
is that so?” One day, he happened to shoot a squirrel with 410A and “It
exploded to pieces! That was the stupidest thing I’ve done while hunting!” Oh
my … Imagining the last moment of that tiny creature was … really sad … They
are petit and lovely, aren’t they? Hm, well, one kind of them are causing a trouble
these days in Yokohama and the south-east of Kanagawa Prefecture.
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| Table Manner of Japanese squirrel |
Japan has three endemic squirrels, Japanese squirrel (Sciurus lis), Japanese giant flying squirrel (Petaurista leucogenys), and Japanese dwarf flying squirrel (Pteromys momonga). I’ll report you my
experience with 2 airborne squirrels later this summer. Today is related to
Japanese squirrel. They live in the forests of not-so-high mountains of Honshu 本州 and Shikoku 四国 Islands. (Hokkaido 北海道 has Hokkaido squirrel and Hokkaido chipmunk
both of which are in the families of squirrels in Siberia.) According to
Wikipedia, an adult weighs about 250-300g with busy winter ears, changes fur
color of their back between summer (red-brown) and winter (grayish white), and
eats while its flowing tail is neatly positioned on its back. Japanese
squirrels are semi-vegetarian with nuts, seeds, and occasional insects. Fortunately,
they are not yet on the red list of endangered species for Japan. In Kanagawa
Prefecture, their home is in Tanzawa 丹沢 and Hakone 箱根. So far, so good, right? It sounds it’s difficult to meet
squirrels in the parks of downtown, doesn’t it? Now you visit or live in cities
of Kanagawa Prefecture, like Yokohama or Kamakura 鎌倉. You
have a relaxing weekend walk in a forest surrounded by houses, or sanctuary of
ancient temples. And you may have a glimpse of small but long-tailed creatures
hopping between the boughs. Squirrels! Cute! Not so fast, please.
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| Last
month, I’ve been to Nagano Prefecture, and found lots of pine cones with food prints of Japanese squirrel. |
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| When a
Japanese squirrel finishes all the pine nuts from a cone, its food print is this. We call it “shrimp fritters.” They can regularly be found in the mountains of Kanagawa Prefecture. |
In
Japanese forests these days, there live the other kinds of squirrels too. For
example, families of Siberian chipmunk and Eurasian red squirrel were first
imported after the 1970s as pets or exhibition animals. They escaped from their
captivity. Their Japanese habitat is still limited now, but National Institute
of Environmental Studies listed them as “invasive” as they can compete with
Japanese squirrel or Japanese dormouse. Moreover, there is an already
established villain in Japanese forests. They are Formosan squirrel which first
escaped to the wild of Oshima Island 大島 in 1935. Since then, they multiplied
to dominate the island’s forest, gnawed electrical wires, and ate fruits of
camellias that are for camellia oil which is the main ag-product of the their
economy. In the early 1950s, Formosan squirrels were started to appear in the
forests of the City of Kamakura. People said they escaped from Samuel Cocking Garden of Enoshima 江の島 (; do you remember we’ve visited there last
summer in “Battle of Sexes”?) where the commercial garden raised them for tourists’
attraction. Since then, they are appearing in the forests of tourism spots near
population centers. What Japanese government is anxious is the possibility of repeating
British experience where Eastern grey squirrel imported during the 19th
century are driving island’s squirrel into extinction and influencing the decrease
in population of wild birds, like dusky thrushes, woodpeckers, and European
jays. Formosan squirrel is listed in Invasive Alien Species Act and prohibited now to be imported, transported or raised in Japan. And Kanagawa prefecture,
especially the south of Yokohama, Kamakura, and Miura Peninsula 三浦半島, is on the frontline of the problem.
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| Formosan squirrel in Segami Citizen Forest |
Formosan
squirrels are bigger than Japanese native. Adult weighs 300-400g with gray-brown
fur which doesn’t change seasonally. They were from Asian tropical rain forests
where lots of fruits are available year-round. The easy access to food and
always hot temperature made them bigger and fecund. They can produce 1-3 pups
whenever. From conception to pup’s leaving the nest, it’s only 80 days, and a
female becomes an adult within a year. But rich ecosystem of the tropics
provides many kinds of predators that keep the population of Formosan squirrel
in check. In contrast, Japan has 4 seasons. Especially during winter to spring,
the forests are freezing cold. Probably because of this, Formosan squirrels in
Japan produce pups only 1-2 times per year. The availability of fruits in
winter-spring forests is strictly limited for relatively large squirrels. But,
hey, next to the Yokohama Citizen Forest is urban ag-lands for veggies of humans.
In addition, this larger mammal throws away highly nutritious foods whenever (and
wherever) convenient. They can even give squirrel foods in the garden of
Tsurugaoka Hachiman Shrine 鶴岡八幡宮, in return for a “cute
selfie together” as a memory of visiting Kamakura. Finally, forests around the
megalopolis Tokyo do not have many raptors, large snakes, or wild mammals, as
in tropical rain forests. i.e. Safe. The Formosan squirrels in Kanagawa are now
like nuclear families in Yokohama or Kamakura. Although they have fewer babies
than in their ancestral land, they nurture the pups in a protected, or
artificial, environment, by commuting to food spots, and let their kids grow
large. The population of adult Formosan squirrels has exploded. After first
spotted in wild in the 1950s, they become common in Kamakura during the 1980s,
and at the turn of the 21st century they are regulars in the
Yokohama’s South Forests, like Maioka 舞岡, Segami 瀬上, Kanazawa 金沢, Hitorizawa 氷取沢, Kamariya
釜利谷, and Nature Observation Forest. That is the
problem for humans.
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| In
cold Japanese forest, Formosan squirrels build a nest with tightly knit twigs to keep inside warm. I think this is one of their houses, found in Yokohama Nature Observation Forest. They are rather too large for crows and look dense. It’s easier to find them during fall to winter when the trees shed the leaves. |
First,
commercial farmers in the east Kanagawa Prefecture found themselves as victims
of meals for squirrels. Producing winter vegetables is a lucrative business in
the suburb of Tokyo. Yokohama is one of the nation’s biggest producing areas
for Japanese mustard spinach, a popular winter green. Such veggies are also
liked by squirrels in winter. Citruses, persimmons, grapes … orchards for such
fruits which could provide nice income during winter holidays attract lots of
hopping and munching squirrels during cold weather. Then, the other incidences
emerged. When Formosan squirrels cannot find meal during winter, they start
licking saps by stripping the barks off from the trees like camellia, Machilus thunbergii, Japanese zelkova,
and maple. Substantial pealing from a tree during winter = gardling is a
standard procedure for forest thinning. The citizen forests and the other
protected areas in the south-east Kanagawa are now having a possible
deterioration of the forest due to the squirrels. The worst case scenario is,
Formosan squirrels cross Sagami River 相模川 and enter Tanzawa and Hakone
where Japanese squirrels live. There, the similar story of Britain with Eastern
grey squirrel can come. Formosan squirrels may win over the Japanese squirrels
and the other animals and birds for food, and could destroy trees that already
have problems with deer. The municipalities of Yokohama, Kamakura, Yokosuka,
Miura, Zushi, and Hayama Town have special budget for controlling the squirrel
population to stop such things to happen. Controlling? Yes, they use mousetrap
to capture, euthanizing by CO2, and incinerating them as industrial garbage. Yuk.
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| This
camellia at the entrance of Enkaisan Hiking Course is literally eaten alive by Formosan squirrels. Could you see a particular kind of scars on its trunk? That’s the sign. |
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| Here
is another. It’s Machilus thunbergii in Yokohama Nature Observation Forest. Both camellia and Machilus thunbergii could withstand the attack of squirrels up to a point. In contrast, those trees which shed their old barks en masse, such as Japanese zelkova and maple, react to gnawing of squirrels with substantial falling of their skin, and often die easily. |
All in
all, it’s a typical tale of unintended consequences born out of careless action
of humans. Formosan squirrels did not come to Japan by their own decision, but
ended up stranded. One ranger for Yokohama Nature Observation Forest is
sanguine. “Well, if there is nothing to eat, it’s natural for squirrels to chew
anything useful for survival, isn’t it?” Yeah … besides, in the suburban forest
of Yokohama or Kamakura, they are certainly substantial and cute mammal that we
hikers can meet relatively easily. Er, well, if you plan to have a selfie with
Formosan squirrel in Japan, please visit the large shrines and temples in
Kamakura. The squirrels there are a sort of city squirrels very relaxed to be
fed by food from tourists. They positively come near you begging something to
eat. If you oblige their request, the animals will give you a chance to have a
photo with them in return. Quid pro quo. Clever … but … at least those which
hopping between the trees in the citizen forests of Yokohama, they are more
cautious and moving rapidly high above the heads of us hikers. Not only shaking
boughs of trees, Formosan squirrels in the forest are also barking in the
woods. In tropical rain forests, when they realize a snake is approaching to
swallow their pups, they call each other with a voice similar to sparrow but in
more urgent, thicker, and louder way to call for collective defense. For
approaching raptors, their voice becomes similar to short-circuited cry of
angry crows to let their fellow to stop moving and to become invisible from the
above. When a larger mammal predator is coming from the ground, they really
bark like a dog, in a very low voice to signal the others to escape higher of trees.
If you walk in Yokohama’s South Forests, and hear something like bird’s call,
but it sounds more robust, that’s the voice of squirrels. One day, I was
welcomed by such dog-like barking from the above near the visitor center of
Nature Observation Forest. Squirrel! So, mean Naomi was doing circles around
the tree where the voice came from. As I enjoy my leisurely circling, the call
got more and more rapid and hysteric, or neurotic, I would say.
“Gwow, gwow,
gwow, gwow, gwow!!!!!!!!!!!!!!”
Hmmmm. Naomi did not have any plan to capture
you to incinerate … though you may not know … The city life of Formosan
squirrel is not easy in Yokohama in the end, I guess.
If you find a problem in the South Forest
of Yokohama, please make a contact with
Office for the Park Greeneries in the
South 南部公園緑地事務所
Yokohama Municipal Government
Creative Environment Policy Bureau 横浜市環境創造局
Phone: 045-831-8484 (I guess in
Japanese only)
FAX: 045-831-9389 (I hope there is
somebody who can read English …)
Yokohama Nature Observation Center at
Yokohama Nature Sanctuary
横浜自然観察の森自然観察センター
Phone: 045-894-7484
FAX: 045-894-8892
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