Bears entered areas near human dwellings despite being adequately nourished, even during years when acorns were scarce in their natural habitats, likely attracted by fruit trees left on abandoned farmland, a recent study in western Japan showed.
The research team, which included the Tokyo University of Agriculture and Technology and Shimane Prefecture's Mountainous Region Research Center, examined the links between acorns, the bears' main autumn food source, and their body fat. Japan's recent rise in bear intrusions has partly been attributed to food scarcity in their natural habitats.
The findings suggest that measures such as removing "attractants" like fallen persimmons and chestnuts and blocking bears' entry routes into settlements are essential, Shinsuke Koike, a professor at the university specializing in ecology, said.
The study examined 651 Asian black bears, one of the two species of bears in the country, that were killed as threats to human neighborhoods or in traffic accidents in Shimane between 2003 and 2018. The team said it is unclear whether the findings can be applied to other areas with different environments.
The bears' nutritional status was measured using three indexes -- subcutaneous, visceral and bone marrow fat -- because when an animal is starving and its nutritional condition declines, it mobilizes fat reserves in a specific order.
Their fat levels peaked in the fall when they feed heavily on acorns ahead of winter hibernation, declining by 62 percent for subcutaneous fat and 39 percent for visceral fat in the spring after hibernation. The fat levels further fell from spring to summer amid tighter food availability.
During hibernation, bears are believed to first burn subcutaneous fat, which is easy to store and metabolize. As their nutritional condition deteriorates, they use visceral fat and bone marrow fat.
Visceral and bone marrow fat levels remained low throughout the year when acorn availability was poor the previous year, while there was no notable difference in subcutaneous fat, the study showed.
At the study site, years of low acorn production by oak trees were typically preceded by years of good or moderate abundance, and bears entering settlements during those periods were "not necessarily compromised" nutritionally.
"These intrusions were likely driven not by a poor nutritional status but by the presence of attractive food sources," said the report published by the Mammal Society of Japan in its journal.
© KYODO
17 Comments
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Mickelicious
Like city foxes (London has 10,000 of them), inland urban seagulls or pigeons before them (originally cliff-dwelling rock doves), attracted - like humans themselves - to more abundant food sources, then?
Toshihiro
Hey, if I was a bear and there was a buffet line that I can eat in for free and with little to no hassle, I'd be going for easier food sources as well. It sure beats digging for chestnuts or taking down the occasional wild boar or deer. Hasn't Yogi Bear taught us anything?
Again, people should be prepared for this. Other northern countries have bears and we hardly hear news of this, let's look at some best practices and see what fits for Japan.
Namorada
Hmm…sounds like Japan should consider planting more variety in their forests. Bring down some of the cedar trees and let nature fill in the gaps with trees and shrubs that might actually produce food sources the bears could eat. Instead, they’ll put more effort and money into identifying target trees in populated areas and remove them.
MichaelBukakis
Hey National Police agency , yes you who issue the hunting licenses.
Guess who’s fault it is when bears attack humans due to overpopulation?
virusrex
Why? the study results point out that the bears are well nourished, they are getting enough to eat in the woods that provide plenty enough food sources. The problems seem to be that fruit trees that become easily available are a powerful attractant even for well fed bears.
The trees mentioned are in abandoned farmland, removing them and letting the land become more like the wild areas surrounding them would not be inherently negative.
At least regarding this article the problem is not overpopulation of bears, just that there are attractive food sources that are easily available to them close to human population centers.
GuruMick
Australia has crocodiles...protected, sharks...protected, poisonous snakes, protected.
I think it is amazing Japan has the wildlife it has, and bears included.
Think outside "the box " and co exist.
kohakuebisu
My impression was that the "few acorns" theory was just a guess by some ojisan, which was then parroted by lots of kohai. There never seemed to be any science behind it. Even anecdotal proof, like sightings of skinny bears.
Anyway, a lesson that its good to study things and not just make assumptions.
fwiw, acorns and chestnuts are mostly starchy carbs, and unlike nuts are very low in fat. This suggests it would be easy to switch to fattening up on carb-heavy fruit.
Vanillasludge
Walk around nearly any rural mountainside town and you will be lucky to run into anyone out and about.
Bears feel secure exploring these areas because there are not enough people to be a threat, but enough to put the smell of food in the air.
In Nagano City there is a spot called Ryozanji, where some of the heads of the dead of Kawanakjima were piled into a mound. Near that spot is an abandoned shrine that is residence to a bear, as evidenced by the repeated digging around the grounds. (I understand they are digging up cicada grubs)
This spot is a two minute walk from a mountainside neighborhood, showing how bold the bears have become.
Sven Asai
Well, we are the only species that values other lifeforms more than ourselves. An aging society with not so many newborns, but all kind of pets have expensive clothes or delicious food, much better than what poor or homeless people have to ingest. And here in this news the wildlife, like boars and bears, they can do what they want, steal harvest from the fields, attack other animals or our villages and cities, hurt and kill us humans, all this with no or only a very few consequences. That is rather sick minded, isn't it, so we really quickly should think about it and change the priorities back a lot, into the direction of our own species and own surviving.
virusrex
Not at all, dogs are well know to put themselves at risk (or even die) to protect their humans.
No or few consequences for whom? the wild animals are hunted frequently when these problem happen.
This makes no sense, not hunting bears or wild boars to extinction is not something we do for mistaken priorities or them being valued above humans, it is not done because of the serious and unpredictable effects on ecosystems that frequently end up causing a much worse situation for humans. Humans are still the main priority (by much) of this strategy.
kurisupisu
Plenty of persimmon trees in Shimane and not enough workers to harvest them.Plenty of low hanging (literally) fruit for both bears and boars to gorge on
mikeylikesit
Interesting. Most of the narrative up to this point has been that bears were hungry because beeches and other trees weren’t producing enough nuts. Turns out that this wasn’t true. It seems to be mainly that rural populations are in retreat, and they leave behind a lot of yummy fruit trees that the bears are happy to take over.
This fits with the pattern that I see in my corner of Japan. Bears have been everywhere in populated areas in the past year or two, not just in the fringe areas along the mountains. Everywhere, too, there are more and more old persimmon and apple trees, grape vines, etc., scattered in personal gardens that people no longer pick. Grandma and grandpa are old. Kids and grandkids live far away in the city. More and more, there’s no one tending the garden.
Malcome Larcens
This seems like an odd conclusion to their study. They were not completely starving but were attracted by fruit trees in cities or close to human habitations. In other words, they were attracted by food. Due to survival instinct, all animals choose the easiest path to food source. They never know when their next meal is going to be, so they eat as much as they can when they can. Are they going to ask apple and persimmon farmers to cut down their trees?
virusrex
What is odd? the whole point was to test the hypothesis that bears were driven to populated areas by lack of food, this was disproved (at least in this location) since bears were well fed, that means this was not the factor for the change in behavior. The factor was the higher availability that attracted bears even without scarcity.
Or as the final quote says:
These intrusions were likely driven not by a poor nutritional status but by the presence of attractive food sources
The findings suggest that measures such as removing "attractants" like fallen persimmons and chestnuts and blocking bears' entry routes into settlements are essential
If anything the trees that would be cut down are those in abandoned farm areas, because it would not make economic sense to take preventive measures to protect them.
fallaffel
Removing fruit trees just to somehow make the land more wild (not sure how this works...) would not necessarily reduce risk of bears coming near humans either. They live in wild areas. It could be a total waste of effort. If the farmland stays abandoned, it will become more natural on its own over time.
OssanAmerica
The National Police Agecy does not issue hunting licenses.
Hunting licenses are issued by the Prefectural Governor under The Wildlife Protection and Hunting Management Law.
The police, under the Public Safety Commission, are only involved in the firearm licensing process.
kaimycahl
@kurisupisu Good point the bears have learned over time to work smarter not harder. Why did when they can go for the low hanging fruit.
Plenty of persimmon trees in Shimane and not enough workers to harvest them.Plenty of low hanging (literally) fruit for both bears and boars to gorge on