1. How common are wild animal attacks compared with other causes of cow deaths?
Wild animals do attack cows, but when you look at all the reasons cows die, attacks are not the biggest cause. [1] A 2015 survey by the United States Department of Agriculture (USDA) found that about 98% of adult cow deaths were caused by things other than predators, such as illness or weather. [1] This means that only about 2% of adult cow deaths were due to attacks by animals. [1]
However, the situation is different for calves. In this survey, calves were separated from adults mainly by weight. For calves, the percentage of deaths caused by predators rose to 11.1%. [1] This number has been increasing over 20 years; in 1995, it was 3.5%. [1] So, while attacks are rare for adult cows, they are more common for calves. This difference connects to the story about Australia later in this article.
2. How did the bear OSO18 repeatedly attack dairy cows in Hokkaido?
In Shibecha and Akkeshi towns in eastern Hokkaido, dairy cows being grazed in fields were attacked continuously starting in 2019. [3] This bear became known as "OSO18" because of the location of the first attack and the width of its front paw prints, which were 18 cm. [3]
Reports say that 66 cows were attacked. [3] It is said that the number of cows that died was almost the same as the number of cows that were only injured. [3] On June 24, 2023, a dairy cow was found dead in a grazing area in Shibecha. By checking the DNA from hair left nearby, officials confirmed it was the 66th cow harmed by OSO18. [4]
On July 30, 2023, a brown bear was killed in Kushiro town. On August 22, the Kushiro General Promotion Bureau announced that DNA testing confirmed this bear was OSO18. [5] The mayor of Shibecha said he was relieved that the economic damage to livestock would finally end. [5] Unlike the statistics in the next section, this damage was caused by one single bear repeating attacks in the same area.
3. Which animals kill cows in the United States?
The same USDA survey shows which animals caused the attacks. The most common attacker was the coyote. [1] About 40.5% of adult cow deaths caused by predators were due to coyotes, and for calves, it was about 53.1%. [1]
Coyotes are animals in the dog family. The survey numbers alone do not explain why more calves are attacked. It is natural to think that smaller calves are easier to attack. On another continent, the attacker might be a lion. A study comparing villages in northern Tanzania found that villages where cows were often attacked by lions tended to keep their cows in larger herds. This study is introduced in another article.
4. How did Australia use poison bait and the Dingo Fence against wild dogs, and what happened to calves?
In Australia, wild dogs, including dingoes, have mainly caused damage to sheep. To protect sheep farming areas in the southeast, a long fence called the Dingo Fence was built. Its total length is about 5,600 km. [7]
So, if farmers put out poison bait to reduce wild dogs, will calves be protected? A study looked at data from 31 farms in Queensland and the Northern Territory, covering 64 farm-years. [8] The frequency of putting out poison bait did not make a clear difference in "miscarriages and calf loss" for mature mother cows. [8] However, the estimate was not very precise, so we cannot say for sure that there is no effect. Instead, losses were higher in years with little rain and in years with very heavy rain. [8] The researchers concluded that killing wild dogs to protect calves is rarely necessary. [8]
5. How do farms protect cows from wild animals?
Besides fences and identifying specific animals, researchers also study how herds behave. One method is using fences. Electric fences work by giving an animal an electric shock when it touches them, teaching the animal not to come close. [9] However, the Kushiro Agricultural Extension Center says that if grass grows more than 50 cm under the fence, electricity can leak. [9] If electricity does not flow, animals learn they can crawl under or jump over the fence. So, cutting grass and maintenance are essential. [9] This advice was written for crop fields, but the way electric fences work is the same in grazing areas.
Another method is managing the herd. There is research showing that in areas with higher danger, cows stayed in larger herds (see another article). However, that study did not check if larger herds actually lower the rate of attacks.
The last method is identifying the specific animal. In the OSO18 case, officials checked the DNA from hair left at the scene to confirm if the same individual was responsible. [4] Knowing which animal attacked allows for targeted measures.
6. How can you investigate wild animal damage to livestock yourself?
Check the websites of your local city, town, or prefecture. Look for pages on "bear sighting information" or "livestock damage." Sometimes, they publish which animals appeared, when, and where.
If you visit a farm, look at the fences. How many strands of wire are there? How many levels? Are there warning signs? Ask the farm staff or read the farm guide to find out what the fence is protecting against. [9] Never touch electric fences, and always read the warning signs. [9]
For those who want to know more, there is a book by Yasushi Fujimoto titled Chase OSO18: The 560-Day Battle with the "Monster Brown Bear" (Bungeishunju, 2024), which records the people who tracked OSO18. [3]