In a lab at the University of Southern California, a mouse notices something is wrong. Its cage mate lies motionless, unresponsive. Without hesitation, the mouse begins to sniff, groom, and then — with surprising determination — pulls the unconscious companion’s tongue out of its mouth. This isn’t an act of aggression. It’s an act of care.
This observation, along with other similar instances, shows that mice, often dismissed as simple creatures, exhibit a remarkable instinct to help their peers in distress. This could mean that the impulse to aid others in need may be deeply rooted in our mammalian heritage.
“They start with sniffing, and then grooming, and then with a very intensive or physical interaction,” Li Zhang, a physiologist at USC and one of the study’s authors, told New Scientist. “They really open the mouth of this animal and pull out its tongue.”
This behavior, which researchers describe as a form of “first aid,” is a deliberate effort to help an unconscious companion recover. In more than 50% of cases, the mice successfully cleared their peer’s airway by pulling their tongue, allowing the unresponsive mouse to wake up faster than those left alone.
A Helping Paw, Driven by Instinct
The study, led by USC neuroscientist Wenjian Sun, involved presenting mice with unconscious, anesthetized, or immobile companions. Some of these companions were familiar cage mates, while others were strangers. The mice were far more likely to attempt resuscitation on familiar individuals, suggesting their actions weren’t purely reflexive.
The researchers also discovered that the mice’s brains lit up with activity during these rescue attempts. Specifically, the medial amygdala — a region involved in social behaviors — became active. There was also a surge in oxytocin, the so-called “love hormone” linked to bonding and caregiving.
This neurological response mirrors what has been observed in larger-brained mammals like dolphins and elephants, which are known to assist distressed members of their species. Dolphins, for instance, have been seen pushing ailing pod mates to the surface to help them breathe. And elephants have been observed supporting injured relatives.
One might wonder if the mice are simply curious about their unconscious companions. But the evidence suggests otherwise. Over five days of repeated experiments, the mice continued to attempt rescues, even when their efforts didn’t immediately yield results.
In one test, researchers placed a non-toxic plastic ball in the mouth of an unconscious mouse. In 80% of cases, the helping mice successfully removed the object. However, when objects were placed in other areas, like the rectum or genitals, the mice ignored them. This strengthens the case that the rodents’ actions were motivated by aiding recovery.
“If we extended the observation window, maybe the success rate could be even higher,” says Huizhong Tao, another member of the USC team.
More instinct than intent
“These findings add to the evidence that an impulse to help others in states of extreme distress is shared by many species,” write neuroscientists William Sheeran and Zoe Donaldson in a commentary accompanying the study.
At the same time, the researchers caution against anthropomorphizing the mice’s behavior. While the actions resemble human first aid, they are likely driven by instinct rather than conscious intent.
Still, the discovery of such behavior in mice — a species not typically associated with complex social care — suggests that the roots of altruism may run deeper than we thought. “This instinctive behavior plays a part in enhancing group cohesion and may be more widely present among social animals than we have seen so far,” Zhang said.
If mice, with their relatively simple brains, can exhibit such behaviors, what does that say about the universality of the impulse to help others? For now, the researchers are focused on understanding the neural mechanisms behind these behaviors. But one thing is clear: even in the smallest of creatures, the drive to care for others is alive and well.
The findings appeared in the journal Science.
