Experts Examine Reports of a Brown Bear and Asiatic Black Bear Hybrid Attacking Humans in Akita

In 2025, bears appeared in human living areas across Japan, terrifying residents. Even the year-end tradition at Kiyomizu Temple of writing a word that represents the year chose “Bear” for 2025.

One factor often cited as a reason bears descend into human settlements is the abundance or scarcity of acorns, a favorite food of Asiatic black bears. In years of poor harvests, bears are said to come down to villages in search of food. However, some studies argue there is no causal relationship between acorn yields and bear appearances. Another view is that bears have learned that they can easily obtain tasty food in human settlements.

Tadaaki Imaizumi, a zoologist well versed in mammals, believes the cause lies in the circumstances surrounding bears (quotations below are Imaizumi’s words).

“Bears would have originally foraged while moving horizontally across certain elevations in the mountains that met the climatic conditions needed for acorns to grow. But the construction of roads in the mountains has obstructed this horizontal movement, effectively confining bears to limited areas. Being forced to move vertically instead has, in part, driven them down into human settlements—this aspect cannot be ignored.”

There are other reasons bears come down into human areas as well.

“Bears probably descended into villages even in the past. But for bears, human settlements used to be frightening places. For example, packs of stray dogs once claimed areas near villages as their territory. When hungry, they would come into villages, and once satisfied, return to the mountains. They could live both near settlements and in the mountains. Dogs are intelligent and choose the easier way to get food.

A single dog can’t compete with a bear, but a pack is different. Hunting dogs used to pursue bears and wild boars in the same way: surrounding the bear as a group, with a dog behind biting its leg; when the bear turns toward that dog, another in front bites its leg. They launch these wave-like attacks. To bears, packs of stray dogs were terrifying. And villages where such dogs lived were frightening places too.

Even among humans, people were told, ‘If you encounter stray dogs, don’t make eye contact and quietly leave.’ But such dogs were eradicated over the past 50 years or so because of the risk of rabies, a disease that was fatal in 100 percent of cases once contracted. In the mountains, there was also the Japanese wolf, a natural enemy of bears, but that species has gone extinct as well.”

Although it has been a long time since packs of stray dogs disappeared, Imaizumi points out that the effects are only now becoming apparent because of bears’ learning ability.

“Cubs brought into villages by their mothers had frightening experiences. Over several generations, they learned that packs of stray dogs were scary, and that villages where such dogs lived were scary too. But after several decades, this changed into ‘There are no stray dogs in villages anymore,’ and ‘If you climb a persimmon tree in a village, you can easily eat delicious persimmons.’

There is a practice called ‘learning release,’ where a bear caught in a trap is deliberately frightened and punished, then released back into the mountains, but it isn’t widespread. Most bears are culled, so the fear of humans is not passed on. I believe changes in the environment surrounding bears have created the current situation.”

Nagano Prefecture was the only place actively practicing this kind of learning release for bears, but in November last year it shifted its policy to exterminating all bears.

As bear sightings increase and people are attacked and terrified, another story has begun to circulate.

In April 2012, brown bears escaped from a bear ranch in Akita Prefecture and attacked employees. It is believed the bears used piled-up snow from heavy snowfall and snow removal within the ranch to climb over the fence. Two people lost their lives, and six escaped bears were shot dead in a tragic incident. In parts of Akita, where bear damage has been occurring frequently in recent years, a rumor has spread:

“One of the brown bears that escaped back then survived, interbred with Asiatic black bears, and has evolved into a murderous monster.”

In Japan, Asiatic black bears inhabit Honshu while brown bears live in Hokkaido, but originally the land was connected and they lived in the same areas. Even today, their habitats overlap in southern Siberia, Russia’s Amur region, and the northern Korean Peninsula, where they are said to coexist by occupying different niches.

If hybridization between Asiatic black bears and brown bears were possible, hybrids should already exist in many places. However, no such facts have been confirmed, and Imaizumi asserts that unless under extreme conditions, hybridization between Asiatic black bears and brown bears is impossible.

“Asiatic black bears and brown bears differ in species, size, and diet. They are different species precisely because they do not interbreed. Even if one were to actively try to crossbreed them in special facilities such as zoos, it would probably be impossible.

I feel the media has been overly sensational in portraying bears as something to fear. People scream when they encounter a bear, and that’s why they get attacked. This talk of an ‘Asiatic black bear–brown bear hybrid’ is itself a manifestation of the fear stirred up toward bears—an illusion born of fear.”

However, when viewed on a global scale, things that should not occur except under “extreme conditions” are in fact happening.

“The hybridization of polar bears and brown bears. This has actually been documented in specimens, and their existence is known. They are said to make up about 1% of the polar bear population. Without ice, polar bears cannot catch seals. Due to the effects of global warming, polar bears are reportedly becoming emaciated and are moving into areas inhabited by brown bears.”

During the Ice Age, brown bears crossed the Bering Strait—then a land bridge—from the Eurasian continent to the American continent and spread southward, dispersing across North America.

However, some brown bears remained in extremely cold regions. Over hundreds of thousands of years, individuals that acquired white fur—making them harder for their prey, seals, to detect—became polar bears. Though they are different species, they can be considered quite closely related.

“It may sound like going back and forth, but if we start from the premise that different species do not interbreed, then this is a serious situation. Polar bears are in an extreme state, and even with brown bears, they think, ‘They’re similar in size and shape, so we have to mate.’

Speciation takes tens of thousands of years, yet global warming has driven hybridization in just a matter of years. If this continues, by 2100 polar bears will become extinct and be absorbed into brown bears.”

Bears are facing various hardships and threats to their survival, and many of these are influenced by humans, fellow living beings on the same planet.