Reports of bear-related injuries to humans have been gaining significant media attention. Prior to 2022, the annual number of people injured by bears nationwide ranged from several dozen to around 100. However, in 2023, the number of victims surged to 219 (including six fatalities). While the figure dropped to 85 in 2024 (82 injured, three dead), 2025 saw a record high of 238 victims (including 13 fatalities). Why did incidents spike so sharply in 2023 and 2025? In fact, both years saw the worst acorn harvests since the 2000 fiscal year. With the scarcity of acorns, many bears descended from the mountains and wandered into human settlements in search of food.
T here are eight species of bears worldwide; two of them inhabit Japan: the brown bear (primarily in Hokkaido) and the Asiatic black bear (mainly on Honshu). Traditionally, a balance was maintained that human settlements and mountain forests remained distinct, each serving as a habitat zone. However, maintaining coexistence between wildlife and humans sometimes requires ensuring that animals have access to sufficient food. Kawasaki Town in Miyagi Prefecture, famous as a hub for “gyutan” (beef tongue) cuisine, has a thriving livestock industry. Farmers there faced a problem: Asiatic black bears were ravaging their fields of dent corn, which is used as cattle feed. To address this, members of the “Association to Protect Asiatic Black Bear Habitats” created fields specifically designated for bears to eat. The idea was that if bears could fill their bellies at the edge of the forest, they would have no reason to risk venturing into the village’s agricultural fields. This initiative—creating fields where bears are free to feed—has been ongoing for a decade. It is true that damage to crops has decreased, and the number of bears being culled is also on the decline.
Do bears—often viewed merely as nuisance animals—offer any potential benefits to humans? I decided to explore this possibility. During hibernation, bears can sleep for several months without eating, drinking, or excreting waste. Remarkably, despite this prolonged slumber, they show almost no signs of muscle or bone deterioration. In contrast, if a human were bedridden and fasting for just one or two weeks, they would inevitably experience a loss of muscle strength. Unlocking the secrets behind the bear’s ability to maintain its physical strength could pave the way for unlocking new human capabilities. We are beginning to catch a glimpse of these secrets. Hibernation triggers significant changes in a bear’s glucose, fat, and protein metabolism. A hibernating bear’s heart rate drops from a normal 40–50 beats per minute to just 8–10 beats per minute, while its metabolic rate falls from 100% to between 20% and 50%. This “energy-saving mode” helps suppress the loss of muscle and bone mass during hibernation. Another key finding is that hibernating bears recycle urea from accumulated urine to produce amino acids. This process, combined with the simultaneous suppression of both protein synthesis and protein breakdown, creates a mechanism that prevents muscle and bone deterioration. If humans could adopt similar biological mechanisms, it might offer a solution to “frailty” in the elderly—a growing concern in today’s society.
