Harvest mice on a wheat stalk. Matt_Gibson / iStock / Getty Images Plus
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Like humans, mice come to the physical aid of their friends when they are hurt, according to new research by scientists at University of Southern California (USC)’s Keck School of Medicine.
The reasons why social mammals seem to help other members of their species when they are injured is something scientists have been exploring.
“[T]his study is the first time we’re seeing a first responder-like behavior in mice,” said Li Zhang, the study’s lead researcher, who is a physiology and neuroscience professor at Keck School of Medicine, in a press release from USC.
The researchers found that mice have a tendency to assist other mice that they know are unconscious. Responses ranged from gentle grooming and sniffing to more forceful actions like biting their peer’s mouth or tongue. As a last resort, the “helper mice” pulled on the tongue of their unconscious friend to dislodge it from their throat and free up their airway.
“The behavior was especially unique due to its similarity to how humans behave in emergency responses,” said Wenjian Sun, lead author of the findings and a research associate at the Zilkha Neurogenetic Institute at Keck School of Medicine. “I had never seen this behavior from mice before.”
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During the study, the neuroscientists put one of the mice under anesthesia to observe how the other mouse would respond. They found that the conscious mouse would spend most of their time at the side of their unconscious cage mate, trying to revive them with what looked like mouth-to-mouth resuscitation, reported USC Annenberg Media.
“Actually, we found this phenomena accidentally,” Sun said. “[The] anesthetized animals’ tongue was protruding out so we started to want to know what’s the meaning of this behavior.”
In over half the cases, the reviver mouse would use the tongue-pulling method, which had an 80 percent success rate.
“We know that humans can do CPR, trying to maintain airways during surgery or any kind of stuff,” Zhang said. “So we interpret the observation as they’re trying to help or trying to revive their group members.”
Co-author of the study Huizhong Tao, a physiology and neuroscience professor at Keck, said the tongue-pulling gestures could not be seen as aggressive, since they were much more pronounced among mice who were familiar with each other and were rarely observed when one of the mice was sleeping or active. Once the mouse who had been unconscious was revived, they also had full use of their tongue.
The researchers found that friendship was important in how the mice handled the situation. Active mice came to the aid of unconscious mice who they had been companions with more often than they did strangers.
According to neuroscientist James Burkett, who was not part of the research team, the resuscitation behaviors stem from neurons that release oxytocin into the brain and show mice’s “altruistic impulse.”
“In this study, we found the oxytocin system plays a great, important role in this behavior,” Sun said. “How the whole oxytocin signaling pathway works in this behavior I think that will be the next step.”
Zhang said the study was the first to show that oxytocin could be a primary factor in social bonding in mice.
“The study’s 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 press release said.
Tao believes the discovery opens the door to new ways of studying prosocial behaviors’ biological functions, including empathy. The research team has plans for longer experiments to find out if the behaviors of mice toward their unconscious peers are even more complex.
“This research suggests many social animals, including humans, might have evolved to help each other in critical situations, improving survival chances and strengthening social bonds,” the press release said.
The study, “Reviving-like prosocial behavior in response to unconscious or dead conspecifics in rodents,” was published in the journal Science.
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