Can stress spread like a virus? What animals tell us.

Can stress spread like a virus? What animals tell us.


Yes, says neuroscientist Tony W. Buchanan, a professor at the University of St. Louis. In 2010, he measured the response of people who simply observed stress in others. Buchanan found that cortisol levels in observers spiked through a phenomenon known as stress contagion—the spread of stress from person to person like a virus.

Now, more researchers are investigating whether this contagiousness is something that can be seen in the animal kingdom.

Scientists hope to find out if stress can pass through channels that are completely different from screeching, screeching and raised juniper. What they learn could inform the treatment of animals and shed light on the nature of stress in humans.

Researchers are “trying to understand how these processes can occur simultaneously in different taxa in birds, in humans, in fish, in mice, so that you have the same phenomenon occurring in very different species that have evolved to a very different level,” Jens says. Pruessner, professor of psychology at McGill University in Montreal.

You’ve probably experienced the stress bug. A friend drops by and spends a few minutes complaining about his job or his partner. Suddenly, even though these aren’t your problems, you’re breathing faster and feeling a little on edge.

That’s because, as you listened, your body quickly gave you adrenaline and cortisol—hormones that mobilize energy stores to run, fight, and finish projects on deadline. Loads of research shows that over time, frequent stress bursts are corrosive to the the body and reproduction.

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Neuroscientist Jaideep Bains studies how stress is imprinted on the brain.

In 2014, Bains began researching in his University of Calgary lab how stress transfers from individual to individual in mice. He discovered that a stressed mouse emits a pheromone from its anal glands, which is then sniffed out by a nearby mouse.

“That kind of makes sense, doesn’t it?” Bains said. “If you think about what a mouse would do – it could be in a field and it’s being chased by a predator, and it goes back to its nest.

“A vocal signal would probably attract attention, but a silent chemical signal, detected only by those very close to you, would be a great way to let others know that there is danger,” Baines added.

Bains found that the neural connections in a mouse that sniffs the stress pheromones will change and become identical to the mouse that first experienced the stressor. Thus, the brain of a mouse that sniffed a stressed mouse appears to have sensed the stressor as well.

Next, “we … asked whether a stressed mouse could transmit information to another mouse and whether that the mouse could then take it away others a mouse,” Bains said. “And it works beautifully. A third mouse shows the same changes in the brain.”

This has implications for humans as well. Like mice, we sense other people’s anxiety.

“We really think of ourselves as individuals who have their own experiences,” Bains said. “And we don’t think much about how the experiences of others and what they go through might also shape us.”

Measuring stress in wild animals is difficult outside the neuroscience laboratory. Most species view scientists as predators and trigger a stress response just by their presence. Animals leave traces of stress hormones in their droppings and feathers, but these are not real-time samples. And capturing animals for blood hormone testing is itself a stressful process for the animals. New technology, however, makes the job easier.

Hanja Brandl from the University of Konstanz in Germany is studying guinea fowl in Kenya using small implanted heart rate monitors combined with solar GPS trackers for observation how stress is transferred from bird to bird. Similar results studies indicate that stressed birds have higher heart rates and, among other things, tend to stick closer to their flocks.

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Brandl and her colleagues are also using video camera traps — cameras triggered by animal movements — and machine learning in other studies.

“Knowing who goes where and how often they feed can indicate that they are stressed,” says Brandl.

Machine learning also gives scientists better data from hours of video. Before deep learning algorithms, Brandl would have to stare at videos for a long time, noting sometimes ambiguous behavior. Now the algorithms accept the fine nuances.

“By giving the computer thousands and sometimes millions of data points, I’m essentially letting the computer decide,” she says.

Scientists have also noticed those groups work together to relieve stress in anxious individual members. For example, vampire bats appease members of their social network by sharing food.

Research is already affecting animal husbandry. Studies have shown that calves recover faster after dehorning when they are allowed to return to their social group, and chicks benefit from being around their mother hens after experiencing mild stress.

“It’s very relatable. … It’s like a child having a little accident on the playground. And with your mother there, you’re probably going to be fine,” says Brandl.

Brandl wrote a review article in the Proceedings of the Royal Society B this year calling for more study of stress transmission from animals.

“More insights from research on animal social systems are needed to unravel the mechanisms and consequences of stress transmission,” she writes. “Identifying the extent to which stress transmission modulates animal groups represents an important avenue of research.”

“Right now we’re just taking the first steps, trying to figure out how important stress transfer really is,” says Brandl. But with more study and more discovery, “we can really fine-tune all the actions that improve animal welfare in captivity and in the wild.”

Bishop Sand is an audio producer at The Washington Post.

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