February 8, 2023 report
Sheep who experience the same shared stress event tend to bond over it
A team of animal behaviorists at the Commonwealth Scientific and Industrial Research Organization, in Australia, has found that sheep who go through shared stressful events tend to huddle together afterward, compared to sheep who do not experience trauma. The study is published in the journal Biology Letters.
Prior study has shown that sheep are able to recognize and remember the faces of other sheep and also of humans. In this new effort, the researchers used that ability to test their reactions to stressful events. Prior research has shown that humans tend to bond when undergoing stressful events. The research teams wondered if they same is true for sheep.
To find out, the team enlisted the assistance of 70 adult female sheep who were unknown to one another. The group was divided into seven subgroups of 10 ewes each. Some of the subgroups were then exposed to different types of stressful events while other groups were not.
Stressful events included being herded by a dog, transported in a trailer, being collared and held by a human, and simulated crutching, in which wool is removed from the legs and tail using electric clippers.
Afterward, all of the sheep were fitted with GPS devices to track their movements and were then herded into a shared pasture. Observation of their behavior showed that initially, the sheep who had become acquainted at the start of testing, prior to division into smaller groups, moved closer to one another. But shortly thereafter, the sheep began to leave such groups to make their way to the sheep with which they had been partnered during the stressful events. Those sheep that had not undergone stressful events remained with their original group.
The researchers suggest that the behavior of the sheep clearly indicates that they had bonded in some way due to a shared stressful event. They also note that none of the sheep were harmed by the experiment—all of the stressful activities were of the kind that sheep routinely undergo as part of their normal lives. The only difference was that more of them happened on the same day.
More information: Hamideh Keshavarzi et al, Shared stressful experiences affect social proximity in Merino sheep, Biology Letters (2023). DOI: 10.1098/rsbl.2022.0396
Journal information: Biology Letters
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