Stress is contagious, and this also applies to animals

Wilderness that was once untouched is rapidly morphing into urban landscapes, evoking changes in animal habitats like never before. Along with climate change, these environmental modifications are ramping up stress factors for animals.

However, a blind spot in research is the exploration of how individual stress levels echo within the group, particularly impacting those untouched by the stressor.

Hanja Brandl, a behavioral biologist from the Cluster of Excellence Collective Behaviour at the University of Konstanz, alongside her colleague, Damien Farine (now at Australian National University) decided to shed light on this phenomenon.

In an exceptional study, the team examined the stress responses of individual birds and how it influences others in the group.

Analyzing animal stress levels

Over three segments of four weeks each, Brandl and Farine exposed certain zebra finches in groups to stressors while recording the ripple effects on both stressed and non-stressed individuals within the group.

Their tools? Stress-induced disruptions and a camera. They also tested for the stress hormone corticosterone in the birds’ tail feathers, adding another layer to their stress analysis.

Stress is a social contagion

What the researchers found was fascinating.

“Our experiments show that stress responses can spread beyond individuals to other members of their social group, even to those who are not exposed to stress themselves,” said Brandl.

In groups with a higher number of stressed birds, the effects on the non-stressed birds were stronger. Non-stressed birds began to behave similarly to the stressed ones, showing changes in activity and behavior.

This imitation of stressed responses suggests that stress in some birds can spread to others, even if they aren’t directly exposed to the stressor.

Stress, social cohesion, and survival

The stress exposure within the group had clear behavioral consequences.

Groups with a significant number of stressed individuals showed a marked decline in activity among the non-stressed birds.

In the wild, this could shrink their exploration and access to resources, thus limiting their survival opportunities.

The researchers also noticed changes in social behavior. Non-stressed birds within such groups held fewer social bonds, putting more weight on existing relationships.

“Stress in a group could impact its social cohesion. At the same time, a reduction in weak social ties would, in turn, reduce the risk of stress transmission,” noted Damien Farine.

Managing stress in wildlife

The insights drawn from Brandl and Farine’s research hold significant implications for conservation efforts and wildlife management strategies.

As human-induced environmental changes escalate, understanding the social dynamics of stress in animal populations becomes crucial.

Managing stress in wildlife not only involves addressing direct environmental pressures but also considering how stress propagates within animal communities.

Conservationists could improve their strategies by promoting conditions that support not only individual well-being but also social cohesion among animals.

This might involve creating habitats that minimize encounters with stressors and promote social interactions that help buffer individuals against stress.

Lessons for humans

Beyond wildlife conservation, the study offers valuable lessons applicable to human societies. Stress is a pervasive aspect of modern life, with individuals often inadvertently affecting those around them.

The concept of stress as a social contagion encourages a reevaluation of community dynamics and mutual support systems.

Just as in animal groups, promoting environments that reduce stress transmission and fortify social connections could enhance collective well-being.

These findings highlight the importance of social networks and community engagement in mitigating stress and promoting resilience not just among animals, but across human societies as well.

Animal behavior beyond stress

Understanding behavior and stress transmission in bird flocks is just one chapter in the larger narrative of animal behavior.

This study also emphasizes the complexity of animal social behavior and its potential impact on survival tactics. It’s no more a solo play; every bird ripple counts.

More details on the study

The study titled “Stress in the social environment: behavioral and social consequences of stress transmission in bird flocks” is recently published in the Proceedings of the Royal Society B Biological Sciences and is available online.

The research was carried out under the auspices of the Cluster of Excellence Collective Behaviour at the University of Konstanz by Hanja Brandl. During the study, Damien Farine was also affiliated with the Cluster of Excellence, as well as the Max Planck Institute of Animal Behavior.

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