‘Bystander’ mice attempt to revive unconscious companions, a new study reveals, suggesting our natural inclination to help others in need runs deep within our mammalian heritage.
The researchers also observed firing in a part of the brain responsible for involuntary functions. Along with boosts in hormonal signals, this appeared critical to the paramedic-like activity.
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While rodent ‘first aid’ involves more biting than the human version, University of Southern California (USC) neuroscientist Wenjian Sun and colleagues found the mice’s tongue-pulling technique actually did enlarge their unconscious peer’s airways, allowing the patient to recover faster.
Another recent study demonstrated this too, and identified a neural circuit that connects the tongue-pulling to rapid arousal in anesthetized mice.
Similar rescue behaviors have long been documented in larger-brained mammals like dolphins and elephants, and mice are known to help others of their kind when they’re trapped, but ‘first aid’ like behaviors haven’t been studied in detail in the smaller mammals before.
We can’t say for sure if the carer mice consciously intend to help, the researchers caution. But that the mice would continue to attempt rescues over five days of repetition suggest the resuscitation events are unlikely just a side effect of curiosity, Sun and team argue.
The researchers also found the mice were more likely to attempt mouse-to-mouse resuscitation on familiar companions over stranger mice.
“That familiarity bias tells you that the animal’s not responding in a reflexive manner to the stimuli that they’re seeing,” University of Toledo neuroscientist James Burkett, who wasn’t involved in the study, told Jonathan Lambert at NPR. “They’re actually taking into account aspects of the situation and the identity of the animal when they’re forming their response.”
In their series of experiments, Sun and his team presented caged mice with dead, unconscious, or immobile companions, some that were known to the potential carer mouse, and others perfect strangers.
In 50 percent of all cases, the conscious mouse pulled the tongue out of the mouth of their unresponsive companions. These mice were all able to recover and start walking again well before those that were left alone did.
“They start with sniffing, and then grooming, and then with a very intensive or physical interaction,” USC physiologist Li Zhang told Chris Simms at New Scientist. “They really open the mouth of this animal and pull out its tongue.”
In 80 percent of cases, the rescuer removed an object scientists had placed in the anesthetized mouse’s mouth. Objects placed in the mouse’s rectum or genitals, however, were ignored.
Resuscitation attempts were also made on dead mice, but not on those just sleeping.
In a third study, researchers from the University of California, Los Angeles, found that when mice were presented with unresponsive peers, the medial amygdala lights up.
This was different from the brain area Sun and colleagues observed becoming active when a mouse interacts with a stressed companion, suggesting the ‘first aid’ behaviors are distinct.
Sun and team identified an increase in oxytocin – a social bonding hormone – in the carers’ paraventricular nucleus in their study as well.
Both these brain regions are known to be involved in caring behaviors.
Neuroscientists William Sheeran and Zoe Donaldson conclude in a commentary about the new studies, “These findings add to the evidence that an impulse to help others in states of extreme distress is shared by many species.”
This research was published in Science.