To think about Japanese deer (Cervus nippon) in forest, it’d be better starting from the behavior of them. They are artiodactyla with slender legs and 4 stomachs. According to Dr. Seiki Takatsuki 高槻成紀, the boss for the Life Museum of Azabu University 麻布大学いのちの博物館, their normal days are almost entirely dedicated to eat and ruminate. On average, an adult deer eats 5-6kg of fresh vegetation daily. They are a typical grazer. Comparing with endemic Japanese serow (Capricornis crispus) which is a browser, i.e. picky eaters, deer eat almost anything of vegetable. Serows eat sasa bamboos and Miscanthus sinensis only in winter when their regular dish of dicotyledon are scarce. Deer simply don’t care. They are also fecund. When they have enough food and a girl Bambi weighs more than 35kg on their 1 year old birthday, deer teenagers start to carry babies. Moreover, they keep delivering a fawn yearly until they reach to 10 or more years old. I.e., a doe has 9 offspring on average. The social life of deer is a harem. An alpha male dominates several pairs of a mom and a kid. They move around together in forest. All suggests when deer stay put for a happy family life, they can rapidly denude the vegetation of the place, or leave only the plants they don’t like.
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| Foot prints of deer |
Let’s return to the 1970s. Animal rights’ movement was gaining momentum in Japan. It was reflected on the management strategy of national parks. By then, ordinary people did not meet wild animals in Tanzawa or Hakone. They simply thought they became so rare as one of the casualties of environmental destruction caused by rapid economic growth. The policy within Fuji-Hakone-Izu National Park 富士箱根伊豆国立公園, and Tanzawa-Oyama Quasi-national Park 丹沢大山国定公園 was protection of the victims of human activities. On the other hand, outside the national parks there still were hunters and other human expansion such as motorization which were menace for the survival of wild animals. The animals simply found refuge within national parks that is roughly 800m ASL and up in Kanagawa Prefecture. Moreover, the afforested coniferous trees were tall enough by the 1970s, which made the forest floor darker. Those mice and hares that competed for food with larger animals lost the habitat and reduced their numbers. Without competitors, deer in particular started to have a protected comfortable life in Kanagawa with lots of food. Well-nourished does constantly gave births to fawns. Around this time, Kanagawa Prefecture began to receive fewer snow falls. Before, it was common in the peaks of Tanzawa and Hakone to be covered by 1m or more snow for months during winter. Slender legged deer are not at all suitable to weigh in deeply snow-covered mountains. Especially for small fawns, snow is deadly. Many actually died during winter in Kanagawa. But since the mid-1970s, Kanagawa has not had deep snow even in the higher altitudes. More girl fawns could now have one year birthday in June and start to mate coming fall. Japan is a small country. The available forest a family of deer can roam freely has a limited acreage even if there were no national parks. By the beginning of the 1980s warmer mountains in Tanzawa had lots of deer harems concentrated in the national park area. They started to eat anything they could find.
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| Yokohama’s
annual average temperature and annual precipitation. Er, well, it’s better to have data for Tanzawa or Hakone. Unfortunately, for these places the older numbers are not retrievable from the homepage of Japan Meteorological Agency. (I guess we have to visit their office next to the Imperial Palace.) Anyway, the mountains are just 40-60km away from the observation point of Yokohama, without obstruction to the flows of air between the places. |
As long as vegetables can reproduce themselves no matter what, the deer concentration won’t be a problem. Instead, from around 1980 the hikers noticed beautiful forests of Fagus crenata in 800m+ ASL of Tanzawa-Oyama began blighted. At the same time, Sasa borealis, which was a typical undergrowth of Fagus crenata in Tanzawa, was eaten by deer and often dead en masse. Then, the research projects started from 1993-1996 (more to them in the next week) confirmed for the first time scientifically a large increase in deer population. Moreover, the scholars realized in Tanzawa flora and fauna were interlinked closely. First, they found Tanzawa was receiving acid rain and photochemical oxidiants emitted by humans from nearby Metropolitan Tokyo. The chemicals weakened the plants in the area. Fagus crenata started to take more time to establish vigorous leaves and tannin which was natural insect repellant. Next came deer. They voraciously ate the plants reachable within the length of their necks. Sasa borealis and other plants including any seedlings were eaten up. The ground around tall trees received direct sunshine and (often polluted) rain, and started to be eroded massively. Fagus crenata is always a home for Fagineura crenativora which found their new dry habitat with less tannin wonderful. Moreover, the denuded undergrowth cannot be a habitat for birds and small mammals that were predators of Fagineura crenativora. The insect increased their numbers explosively, and devoured rapidly all the leaves of Fagus crenata. Unable to photosynthesize, the trees were starved to death. Other species of the already established tall trees may have escaped the fate of Fagus crenata, but their seedlings in Tanzawa-Oyama Quasi-national Park were not so lucky. The variety of forest floor plants became very limited at best, and the forest consisted only of old trees.
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| Deer cause damages to forests not only by eating but also by grinding their antlers. Their behavior can practically thin trees by stripping away their cambium. Last winter Dr. Takatsuki introduced us an incident in Oku-Nikko 奥日光 where centuries-old cedars died-back due to deer grinding ... I hope this still young cypress in Tanzawa can survive the damage done in this way … |
From around 2000, Japanese rural area began to notice unprecedented influence of deer and the other wild animals. Dr. Takatsuki constructed a picture using the data from Ministries of Environment and of Agriculture, Forestry and Fisheries and concluded the acreages started to grow exponentially for the agriculture and forestry lands that suffered damages from deer. The number of deer caught by hunters also sky-rocketed, along with the number of locations they were captured/killed. His colleague of professional botanists were/are witnessing drastic impoverishment in their field including massive landslides. The red-listed plants, such as Viola kitamiana, were/are nearing the extinction because lots of Japanese/Yezo deer eat them. Ozegahara Marshland 尾瀬ヶ原 has started to dry-up because deer, wild boar and the other wild animals with increasing population forage the leaves and roots of the plants in the area. Okutama Mountains 奥多摩 in Tokyo were/are suffering the landslides as deer denuded the steep slopes, which is now a serious problem of water supply to the capital city. The trend continues today. These days, collecting wild spring herbs in Japanese mountains is a sort of desperate act. The season for herbs coincides with the time when now-numerous mama bears come out from hibernation with their cubs. Hearing nation-wide news for unlucky herb collectors who were killed by Asian black bear or brown bear has become a routine. Exploded boar population dominates the evacuated community around the Fukushima Dai-ichnuclear plant, and ravaged the land. The City of Kobe that is practically pasted to Rokkoh Mountains 六甲山地 has now a boar problem. Gourmet boars attack old ladies carrying cakes and puddings from famous patissiers, because the animals know the grandmas have wonderful sweets. Clever Japanese macaques invade into commercial orchards, and even rice paddies, just before the harvest and eat up the precious crops that would have sustained the farming households for the next year …
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| A
billboard near Hinata Yakushi Temple 日向薬師 in
Tanzawa. It is warning the visitors the place is monkey infested. “Please do not give bait to monkeys, and be sure to carry the left-over of your lunch home. Thank you for the cooperation to reduce agricultural damage by monkeys in this area.” |
The effect is not necessarily found directly from wild animals, but diseases. Some have started to worry a spread of Lyme diseases in Japan due to roaming herds of deer with ticks. More visibly, thanks to the skyrocketed number of deer and hikers from cities, especially Tanzawa is now infested by blood-thirsty land leeches. It is not uncommon for people to show allergic symptoms with a leech-bite. Vampire leeches keep clinging to mammals to suck blood until they drink enough. Unless a prey notices and takes off the leeches from the body, they will be carried anywhere the animal go. Even if you stamp them hard, those slimy creatures simply survive. To stop spreading land leeches, when you find them in Japanese mountain, please kill them immediately by (1) showering them with salt, vinegar, ethanol or DDT, (2) (not recommended) roasting them by fire with at most caution for preventing wild fire. Those uninitiated hikers did/do not do these important tasks. Moreover, the leeches are hermaphrodite and lay thousands of eggs immediately after finishing their blood meal. Suppose you simply shake them off at a bus stop returning from a weekend hike, without terminating them. The formerly peaceful bus stop is now a home for many leeches. And don’t ask deer to deal with the problem. Thus, the larger the number of deer and hikers becomes, the wider the infested area is. Actually, around the turn of the century, some parts of Chiba Prefecture began to observe farmers giving up lands due to overwhelming land leeches carried by exponential growth of deer’s and hikers’ population. Luckily or not, Kanagawa Prefecture is more urbanized than Chiba, but the problem is serious nonetheless.
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| A leech
showered by ethanol to death. Have you noticed it’s a sort of chubby? It sucked lots of blood from a guy, and became like a pea like this. |
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| If you
find yourself a prey for leeches, (1) peel them off with your finger, (2) kill them immediately, (3) on site, squeeze out the saliva of leeches and wash the wound by clean water or ethanol, and (4) if you carry anti-histamine cream, apply it to avoid itches. You’d better visit doctors afterward. Having said that, the most effective strategy against land leeches is not being sucked. Especially in Tanzawa from May to October, always cover your skin with something difficult for leeches to stick. Vinyl garment is not advisable. In a sunny day, they crawl up from the ground. If it rains, they shelter themselves under any tree leaves, and drop down to a prey when we pass below them. The first line of defense is spraying leech repellent your feet and legs, and if it rains around your shoulders and neck too. The standard chemical for this purpose is still DDT, but I prefer the product of this photo as it’s DDT-free. |
At least in Kanagawa, the system to cope with this 21st century ecological problem has been in place and evolving. Our prefecture is actually the leader for this matter in the nation, although we can say for sure the problem is not at all solved even in our backyard. Next week, I tell you what Kanagawa Prefecture is doing these days, including hiring for a new job. For some of you who are interested in pursuing this particular career in Japan, I report you the terms of reference next week. It seems to me the vacancy ads for the posts are increasing nation-wide these days …
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| Sorry
for this out-of-focus photo … They are the stags I’ve met last March in Mt. Oyama. They were actually fighting. |
If you find environmental problems in
mountains of Kanagawa Prefecture, please make a contact to
Kanagawa Nature 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/
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