HOKKAIDO, Jun 07, 2025 (News On Japan) - A bear known as OSO18, which attacked more than 60 cattle in eastern Hokkaido, has been revealed to be an unusually extreme carnivore, primarily feeding on Ezo deer.
Nicknamed the "monster" and "ninja" bear, OSO18 terrorized dairy farmers in eastern Hokkaido before being killed in 2023. Researchers from Fukui Prefectural University and other institutions analyzed the bones of approximately 600 bears across Hokkaido, including OSO18, and discovered that while bears are typically omnivorous, OSO18 consistently ate Ezo deer and other animals from age 3 until it was killed at age 9.
"It’s normal for bears to eat deer when they come across carcasses, but OSO18 was feeding on them year-round," said Associate Professor Matsubayashi Jun of Fukui Prefectural University.
Although the reason behind this behavior is unclear, similar eating patterns were also observed in other bears culled near Shibecha Town, where OSO18 was active.
OSO18 was a brown bear that became infamous across Japan for a series of violent cattle attacks in eastern Hokkaido, particularly around the town of Shibecha in the Kushiro region. The name “OSO18” was derived from the code assigned by authorities: “OSO” for the Osotsubetsu area where it was first detected, and “18” indicating it was the 18th bear recorded in that area. Sightings and DNA traces linked to OSO18 began around 2016, and over the following years it was confirmed to have attacked and killed more than 60 head of cattle. This made it one of the most destructive bears in modern Japanese history, and it quickly gained nationwide attention. Locals and media dubbed it a “monster” or “ninja” bear due to its elusiveness and ability to evade numerous capture attempts despite the use of traps, drones, infrared cameras, and even sniper patrols.
OSO18 developed an unusually long track record of livestock predation, which is rare for brown bears, as most avoid prolonged contact with humans or large livestock. It operated mainly under cover of darkness, rarely leaving behind clear tracks or images, making it extraordinarily difficult for authorities to predict or trap. The bear also demonstrated unusual behavior for its species—while brown bears are generally omnivorous and opportunistic feeders, OSO18 had developed a sustained preference for hunting large animals, especially cattle. Some experts speculated that the bear had developed learned behavior, possibly linking the sound of electric fences or the smell of ranch areas with easy prey. Its attacks often left behind barely eaten carcasses, leading to theories that the killings were driven by more than just hunger.
After years of failed attempts to track and kill it, OSO18 was finally shot and killed in July 2023 by a licensed hunter working in coordination with local authorities. The confirmation came through DNA testing, which matched the bear to previous cattle attacks.
Related: Killer 'Ninja Bear' meat not so grisly
Source: 北海道ニュースUHB
