Mice Can Attempt to Revive Their Companions: The Social Instinct Behind Oxytocin

In human society, when someone suddenly collapses and loses consciousness, people often instinctively attempt first aid to wake them. This raises an intriguing question: is this type of “revival response” unique to humans? Do animals also display specific social behaviors when one of their companions becomes unconscious? To explore this question, researchers examined how laboratory mice react when encountering companions that have become unconscious or died.

Mouse behaviors toward an unconscious peer（Courtesy of Sun W et al. (2025). Science ）

When a mouse encounters a cage mate that has been anesthetized into unconsciousness, its behavior does not remain limited to simple sniffing or passive observation. At first, the mouse approaches the unconscious companion, sniffing it and gently grooming its fur. If the companion remains unresponsive over time, the behavior escalates into stronger physical stimulation. The helper mouse may bite the partner's mouth, bite the tongue, or even pull the tongue outward.

These behaviors are not random. They follow a clear temporal sequence. When a companion has only recently become unconscious, mice initially respond with gentle contact. As the unresponsive state continues, more forceful oral stimulation gradually appears. Once the unconscious mouse begins to move again, these behaviors immediately stop. This pattern indicates that the actions are closely linked to the partner's continued lack of responsiveness.

Interestingly, these revival-like actions are not limited to companions rendered unconscious by anesthesia. When mice encounter a recently dead cage mate, similar oral and tongue interactions still occur. In contrast, when the partner is merely sleeping, these intense behaviors are rarely observed. This difference shows that mice are capable of distinguishing between temporary unconsciousness and normal sleep, adjusting their behavior according to the partner's condition.

Experimental observations also suggest that these actions may produce genuine rescue-like effects. When a mouse pulls its companion's tongue outward, the opening of the airway becomes significantly larger. This resembles medical procedures used to prevent airway obstruction in unconscious patients, where the tongue may block breathing. In addition, if researchers place a small object inside the mouth of an unconscious mouse, another mouse often removes it by biting around the mouth or pulling the tongue. In doing so, the helper effectively clears potential airway obstruction. Mice that receive such stimulation tend to regain movement sooner than individuals left alone.

At the neural level, these rescue-like behaviors are closely associated with activation of the oxytocin system. Oxytocin neurons are primarily located in the paraventricular nucleus of the hypothalamus, a brain region deeply involved in social behavior and empathy in mammals. When a mouse encounters an unconscious companion, oxytocin neurons in this region show a clear increase in activity. Artificially stimulating these neurons enhances grooming and oral stimulation behaviors, whereas suppressing their activity or blocking oxytocin signaling significantly reduces these responses. Measurements of calcium signals in the brain further reveal that the collective activity of oxytocin neurons can accurately distinguish whether a companion is responsive or unresponsive.

Social familiarity also plays a critical role. In experiments, mice display strong revival-like behaviors only toward familiar cage mates. When encountering unfamiliar mice, these intense actions are largely absent. This familiarity bias highlights the importance of social bonds in empathy-like and helping behaviors. Sex differences appear relatively minor. Both male and female mice respond to familiar unconscious companions in similar ways, although females show slightly greater initiative when interacting with unfamiliar individuals. Moreover, when the same experiment is repeated once per day over five consecutive days, the strength of these behaviors does not decline. This persistence suggests that the actions are neither driven by curiosity nor diminished through repeated exposure. Instead, they represent a stable instinctive behavioral pattern.

From an evolutionary perspective, such revival-like responses likely carry clear survival advantages. In social animals, assisting group members who have become unconscious or endangered may increase the likelihood that those individuals recover, thereby strengthening group cohesion and improving overall survival. Because the oxytocin system is highly conserved across vertebrates, these behaviors may not be unique to mice or humans. Rather, they may reflect a fundamental biological foundation shared by many social species.

These findings offer a glimpse into the deep evolutionary roots of empathy and helping behavior, suggesting that the impulse to assist an incapacitated companion may arise from ancient neural mechanisms embedded within the social brain.

Author: Shui-Ye You

Reference:

Sun W et al. (2025). Reviving-like prosocial behavior in response to unconscious or dead conspecifics in rodents. Science.

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