Mice Exhibit Altruistic Actions Towards Injured Companions

Humans aren’t the only species that help their injured peers—mice might do it too. A recent study from the Keck School of Medicine at USC, published in Science, suggests that mice may exhibit first responder-like behaviors when encountering unconscious companions.

Emergency Response in Mice

Researchers have long studied why social mammals assist injured individuals of their species. This study is the first to observe such behavior in mice, revealing a fascinating parallel to human emergency response.

“There are numerous factors that determine empathetic behavior and social bonding in mammals. But this study is the first time we are seeing a first responder-like behavior in mice.”

Li Zhang, Study Principal Investigator and Professor of Physiology and Neuroscience, Keck School of Medicine, USC

The study found that mice tend to help unconscious mice they recognize, responding with actions ranging from gentle sniffing and grooming to more assertive attempts to revive them, such as biting or pulling their tongues.

“The behavior was especially unique due to its similarity to how humans behave in emergency responses. I had never seen this behavior from mice before.”

Wenjian Sun, Study First Author and Research Associate, Zilkha Neurogenetic Institute, Keck School of Medicine, USC

Helper Mice and Airway Assistance

The researchers initially observed this behavior by chance during an unrelated experiment. Just as humans assess and respond to an unconscious individual, the “helper mice” focused on their peers' mouths and tongues, a response that appeared to improve airway function and accelerate recovery.

Huizhong Tao, a co-author of the study and professor at the Keck School of Medicine, clarified that this tongue-pulling behavior is not aggression. The social behaviors were far more common among familiar mice and rarely observed when one mouse was simply asleep or active. Once revived, the unconscious mice exhibited normal tongue function, reinforcing the idea that their peers were genuinely aiding them.

The Role of Oxytocin

Using advanced neural imaging and optogenetics, the study explored the brain mechanisms behind this behavior. One of the most striking findings was the activation of oxytocin neuropeptides, commonly known as the "love hormone." Oxytocin is widely recognized for its role in trust, bonding, and affection.

“This is the first study to suggest that oxytocin may play a key role in social bonding among mice. The results deepen our understanding of animal behavior and highlight the oxytocin system’s significance across vertebrate species.”

—Li Zhang

Implications for Social Behavior and Evolution

Looking ahead, the research team plans to conduct longer-term studies to determine whether mice exhibit even more complex responses to unconscious peers. Tao believes these findings open exciting new directions for understanding the biological roots of prosocial behavior, including empathy.

This research suggests that many social animals, including humans, may have evolved mechanisms to assist one another in critical situations, strengthening survival and reinforcing social bonds.