Mice offer first aid to unconscious companions

Mice sometimes surprise researchers in the lab. When a young mouse spots another lying still, it may paw at its comatose friend, chew on its snout, or even yank its limp tongue aside.

Li Zhang at the University of Southern California and his colleagues have been looking into these interactions.

They captured footage of lab mice confronting a familiar cage mate that had been anesthetized and was unresponsive.

Rescue behavior in mice

“They start with sniffing, and then grooming, and then with a very intensive or physical interaction,” related Li Zhang.

Scientists observed grooming and mouth-focused nibbling. Some mice targeted the unmoving partner’s mouth area, pulling its tongue out in an attempt to clear the airway.

These same actions occasionally turned up in mice that were interacting with companions that had passed away.

Researchers noticed how these stereotypical gestures tapered off once the still mouse revived and regained motion.

They also found that a mouse gave more attention to an unresponsive peer that was recognizable than to one that was a stranger.

This distinction suggests that familiarity plays a role in prompting these rescue-like behaviors.

Insight from other animals

Large mammals such as chimpanzees, dolphins, and elephants have been recorded aiding group members that are in trouble.

Some dolphins have guided a distressed pod mate to the surface so it could breathe, which has long intrigued scientists who study social behaviors in marine animals.

Elephants have also been known to support injured relatives. These examples suggest that lending a helping hand isn’t always limited to humans.

Rodents, however, can be trickier to monitor in the wild. Mice prefer concealed spaces and often scatter at the slightest hint of danger. That makes it challenging to film them tending to an ailing group member outside the lab. 

Role of oxytocin in rescue behavior

These rescue-like gestures appear linked to the presence of oxytocin, a hormone that influences bonding in many species. The new study detected active oxytocin-releasing neurons in the amygdala and hypothalamus.

These brain regions, known to handle emotion and social behavior, lit up when mice recognized a cage mate in distress. 

“If we extended the observation window, maybe the success rate could be even higher,” said team member Huizhong Tao, also from USC.

Additional evidence showed that turning off these neuron signals or blocking their ability to dispatch oxytocin reduced the mice’s apparent attempts to help.

Activating the same neurons produced more grooming and nibbling.

The link between this hormone and nurturing conduct has come up in past research, supporting the view that many mammals share some wiring for caring.

Importance for group survival

Scientists think these behaviors might help keep social groups together and improve survival. Young mice that responded to a motionless mate saw that partner bounce back to normal sooner than those left alone.

That small difference might affect how groups function in their natural habitats, where every second can be a matter of life or death.

Some researchers say caution is needed when drawing big conclusions. Animals often do things that look human-like, but motives can be complicated.

Still, these lab findings give hints that even small creatures might care more about their companions than we once believed.

Bigger picture

Many animals rely on social bonds for carrying out different activities, from defense to nurturing infants.

This study raises the possibility that more species have built-in behaviors that benefit the whole community.

Researchers suspect that similar patterns might exist in other species but remain unnoticed because of how tough it is to observe these moments in the wild.

Oxytocin is a hormone found in many vertebrate species and the researchers suggest that it could underpin an innate emergency response to assist an unresponsive group member.

This revival behavior may thus be widely present, particularly among social animals.

The discovery that mice act as tiny caregivers prompts new questions. Scientists plan to test if there are variations among different strains of mice.

Some want to see if environmental factors, such as stress or crowding, affect how likely mice are to step up for a comatose mate.

The study is published in Science.

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