An international collaborative research team including Project Assistant Professor Akino Inagaki and Professor Shinsuke Koike of the Graduate School of Global Innovation Research, Tokyo University of Agriculture and Technology, and Associate Professor Maximilian L. Allen of the University of Illinois (concurrently Project Associate Professor, Graduate School of Global Innovation Research, Tokyo University of Agriculture and Technology) has succeeded in recording a scene of an Asiatic black bear preying on a Japanese sika deer that had been caught in a trap in the mountains of Nikko City, Tochigi Prefecture.

 In Japan, deer are causing serious damage to agriculture and forestry and altering ecosystems, so deer are being captured all over the country. An increasingly popular capture method is the "snare trap," which involves tying the deer's legs with a wire rope to prevent them from moving. This method is becoming more popular because it is easy to transport and set up, and is cost-effective. They are sometimes set up not only in the mountains, but also near residential areas and farmland. In recent years, there have been reports of deer caught in these snare traps being eaten by bears in Honshu, but there were no concrete records of this happening.

 In May 2024, a person who was working to capture deer as a measure against the increased deer population set up a trap and an automatic camera for recording in a mountain forest, and about 5 minutes after an adult female deer was caught in the trap, an adult bear attacked and preyed on it. The bear appeared at least four times over the two days before the deer was retrieved by the capture worker, and ate almost all of the deer's internal organs.

 Although bears will sometimes eat deer carcasses they find, it was thought that healthy deer would not be hunted. However, the images captured showed bears attacking and preying on adult deer that showed no signs of weakness. This is the first such finding in the world, and it raises the possibility that capturing deer as a measure against animal damage may provide bears with a new food resource. In the future, it will be necessary to clarify in detail the frequency of occurrence and how bears find deer caught in traps.

 In addition, this series of records has highlighted the need to check the frequency of traps, as deer are attacked within a short time of being caught in the traps. Furthermore, because the deer's feet are tied to trees and other objects with wire ropes, they return to the site multiple times to hunt, raising the risk of encounters with patrolling predators and ordinary residents. There is also the possibility that wild animals approaching to catch deer left over from bears may accidentally get caught in other snare traps. In light of these issues, the research team believes it is necessary to consider capture methods that minimize the danger to both humans and wild animals.

Paper information:【Ursus】Documentation of an Asiatic black bear preying on a living sika deer caught in a leg-hold snare trap

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