Increasing Carnivorous Behavior in Bears Raises Concerns About Human Safety

Bears tend to fixate on foods whose taste they remember, and this can make them more aggressive

Incidents of people being attacked by bears in residential areas have been occurring nationwide.

In Hokkaido, on the 12th of last month, a male newspaper delivery worker was attacked and killed by a brown bear in a residential area of Fukushima Town. The prefectural government issued a brown bear warning for the entire town to prevent further human casualties. This is the first time such a warning has been issued since the alert system was established in 2022.

Six days later, on the 18th, the bear in Fukushima Town was culled by hunters in a residential area about 800 meters from the location of the previous attack. Further DNA analysis of the bear’s fur confirmed that it was the same male bear that, in 2021, had attacked and killed a woman in her 70s while she was working in a field in the same town.

DNA analysis revealed that the bear responsible for the human attack four years later was the same individual, prompting experts to say that such a case is unprecedented. Professor Kiyokazu Sato (wildlife ecology) at Rakuno Gakuen University called it the first case we’ve ever documented, and commented:

“I believe that the careful on-site investigations conducted at the time of the previous incident, along with the collection and analysis of DNA samples, led to this new discovery.”

Regarding the bear in Fukushima Town that attacked two residents after a four-year gap, experts have suggested that it might have targeted humans during the attack or recalled the experience of attacking humans while repeatedly appearing in residential areas in search of food. Professor Sato shared his perspective:

“In my view, if the bear remembered attacking humans four years ago and had been fixated on people, it would have appeared frequently in residential areas during that period, and human-bear incidents would likely have occurred in the meantime.

Bears tend to fixate on foods whose taste they remember, and they can become aggressive in obtaining or defending those foods. It seems unlikely that a bear, which spent four years quietly away from human settlements, would suddenly recall an attack on a person.”

In other words, the bear was not intentionally targeting humans in residential areas.

“In Fukushima Town, before and after the incident, there were reports of bears raiding local garbage sites. The bear had been repeatedly drawn to these sites at night, suggesting that it was more fixated on the garbage than on humans.

We don’t know exactly when the bear began raiding garbage, but at some point, its behavior likely shifted from merely appearing in town to seeking food in garbage.

This change should have been treated as a critical situation, but it was handled as if it were routine. As a result, the bear accumulated successful experiences, which likely escalated its behavior to the point of venturing into the city center.”

The Fukushima Town bear approached hunters and police officers from the grass, and was culled at a distance of five meters. Bears are generally considered cautious, but was this one unafraid of humans?

“At first, the bear probably tried to avoid humans, which is why it appeared cautiously only at night.

Then it encountered garbage that smelled good and tasted it, learning that the human world had special foods. Its repeated scavenging at garbage sites led to a loss of caution.

For a bear, human food must be irresistibly tasty, to the point of overwhelming its awareness of the surroundings.”

The tendency toward carnivorous behavior is increasing

Professor Sato points out that bears’ wariness toward humans is itself changing.

“Bears born and raised near human settlements are more accustomed to people than those deep in the mountains, simply because they encounter humans more often.

We humans, too, act with maximum caution around bears without chasing or threatening them. As a result, bears living near settlements accumulate experiences that humans are not so scary, and their wariness toward people tends to be relatively weak.

This in itself is not necessarily a bad thing. However, when a bear with little caution encounters things like garbage or crops, its behavior tends to become bolder, increasing the likelihood of becoming a dangerous bear. That’s something we need to be careful about.”

What about changes in diet? Brown bears are omnivorous, and their main diet typically consists of nuts, plants, and insects.

Professor Sato notes: “The local media often ask me if bears have become more carnivorous, and I do feel that is the case.

Since the late 1990s, the deer population has increased rapidly, resulting in a large number of easily accessible deer carcasses for bears. Most bears in eastern Hokkaido have eaten deer, and some individuals even survive primarily by feeding on deer.

The high density of deer is gradually spreading from eastern Hokkaido to central and southern regions. Recently, bears in southern Hokkaido may also be eating deer.

I wouldn’t say the bears’ diet has fundamentally changed, but the opportunities to consume animal-based food have increased, so it’s fair to say there is a trend toward more carnivorous behavior.”

However, an increase in deer is not necessarily beneficial for bears.

“Several factors have contributed to the rise in deer populations. Shorter snow seasons and reduced snowfall due to warming have decreased winter deer mortality. Conversion of primeval forests into farmland expanded their feeding grounds, and the extinction of wolves, a natural predator, made survival easier.

As a result, the soft grasses that bears preferred to eat from spring to summer are mostly consumed by deer. Summer through autumn is when bears are the hungriest, so it’s only natural they would target deer when they find them.”

Neither the authorities nor the residents are willing to put much effort into steady, long-term measures

Since October 2023, Hokkaido has been reviewing the “Brown Bear Management Plan” (originally formulated in March 2022) and revised it in December last year, shifting its policy toward active culling to reduce bear populations.

“The approach has shifted to strengthen culling not only of problem bears but also those living near residential areas in order to reduce incidents. ‘Spring management culling’ during the period of lingering snow will be promoted, and financial support will be provided for hunter training and securing personnel. I believe a clear trend toward promoting culling has now been established.”

According to Hokkaido authorities, 1,804 brown bears were captured in the prefecture in fiscal 2023, marking a record high. The number of captures in fiscal 2024 is projected to drop significantly to around 700, based on provisional figures.

“Although the number of captures in 2024 may not increase substantially, a fair number of cubs must have been born, so the bear population might have slightly rebounded this year. However, I also expect that capture numbers could rise again,” the authorities said.

Hokkaido aims to reduce its estimated brown bear population by 35% over the next ten years—from 12,200 in 2022 to around 8,000 by the end of 2034. But is this achievable?

“Strengthening captures could reduce bear appearances, but it’s not something that will happen easily. Of course, capturing bears is necessary, and I believe municipalities are committed to doing so. However, both administrative bodies and residents often don’t put enough effort into grassroots measures, such as clearing bear pathways or installing electric fences. That’s a major issue. I’ve repeatedly emphasized this, but progress is slow”

Neglecting overgrown areas that reduce visibility or leaving out trash the night before can increase the risk of bear incidents. Yet residents in regions with frequent bear sightings seem not to fully recognize this risk. Professor Yoshikazu Sato emphasizes.

Administrative roles are also critical.

“Currently, most municipal offices don’t have staff dedicated exclusively to bear or deer management. Staff are usually multitasking with other departments and often only respond during bear appearances or culling events. Moreover, these staff may lack expertise in wildlife, so appropriate measures cannot be expected.

It’s not necessary for staff to specialize only in bears—they should handle all wildlife issues, including deer, raccoons, and crows. Local mayors and council members need to seriously consider allocating such personnel. Furthermore, the Hokkaido government and subprefectural offices should provide stronger support—for example, by urging municipalities to implement measures or sharing information about effective initiatives. This kind of support is necessary to strengthen everyday regional measures.”

After incidents in Fukushima Town, the authorities received a flood of calls and emails—from people demanding exterminate the bears or cull them quickly to messages saying poor bears or don’t kill them—reflecting a mix of outrage and misguided assumptions. Many locals living in bear habitats is likely frustrated by such thoughtless complaints from outside the region.

“In Hokkaido, bear incidents can occur anywhere. We can’t expect to eliminate the problem entirely. As residents, the most important thing is to continue creating bear-resistant communities and minimize bear incursions. That’s what matters most,” Sato concludes.

▼Yoshikazu Sato is a professor of wildlife ecology at Rakuno Gakuen University, born in Tokyo. He belonged to the “Hokkaido University Brown Bear Research Group” during his time at Hokkaido University’s Faculty of Agriculture. He currently serves as chair of the Hokkaido Brown Bear Protection and Management Committee and as a member of the Science Committee for the Shiretoko World Natural Heritage Site. He is also involved in grass-cutting activities in the Ishiyama area of Minami Ward, Sapporo. His publications include Urban Bear: Facing the Bears Next Door (University of Tokyo Press).