In new lab experiments, scientists at the University of Southern California showed that when mice encountered a familiar social partner in a state of unconsciousness caused by anesthesia, they displayed distinct and consistent behaviors toward the partner, escalating from sniffing and grooming to more forceful actions such as biting the partner’s mouth or tongue and pulling its tongue out.
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Mice have their own form of ‘first aid’ practices to help other mice in need. Image credit: Sun et al., doi: 10.1126/science.adq2677.
“There are numerous factors that determine empathetic behavior and social bonding in mammals,” said Professor Li Zhang, a researcher at the University of Southern California.
“But this study is the first time we’re seeing a first responder-like behavior in mice.”
The new study shows that mice tend to help other mice they know are unconscious.
Their response ranges from gentle sniffing and grooming to more forceful actions such as mouth or tongue biting, before finally escalating to pulling the tongue out of the unconscious mouse.
“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,” said Dr. Wenjian Sun, also from the University of Southern California.
Interestingly, the scientists first witnessed the rehabilitative behavior among mice paired together in an unrelated study.
When humans encounter an unconscious individual, the emergency response is varied, including assessing the situation, checking responsiveness, calling for help and performing cardiopulmonary resuscitation (CPR) on an individual.
“The urgency with which ‘helper mice’ target the mouth and tongue of their unconscious peers appears to improve the airway of their peer and lead to a faster recovery,” said University of Southern California’s Professor Huizhong Tao.
“We learned the act of tongue-pulling between mice in this study could not be interpreted as an aggressive gesture.”
“The social behaviors in the study were significantly more pronounced among familiar pairs of mice and were rarely seen when one of the paired mice was simply sleeping or active.”
“Furthermore, after the unconscious mice regained consciousness, they had regular use of their tongue.”
In the study, the authors utilized advanced neural imaging and optogenetics to investigate the neural mechanisms behind the social behaviors of the helper mice.
“One of the most intriguing aspects of our neural observations was the discovery of the activation of oxytocin neuropeptides,” Professor Zhang said.
“Oxytocin is widely known as a hormone that plays a crucial role in social bonding.”
“Oxytocin is sometimes called the love hormone because it is associated with feelings of trust, bonding and affection.”
“This was the first study to show oxytocin may also be a key factor in the social bonding in mice.”
“Our findings not only enhance our understanding of animal behavior but also highlight the critical role of the oxytocin system, which may also inform social behaviors across vertebrate species.”
The results appear in the journal Science.
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Wenjian Sun et al. 2025. Reviving-like prosocial behavior in response to unconscious or dead conspecifics in rodents. Science 387 (6736); doi: 10.1126/science.adq2677
