Voles Console Friends and Display Oxytocin-Based Empathy
A new study shows for the first time that rodents console others in distress
Posted Jan 24, 2016
Rodents are fascinating animals and the more they are studied the more we learn about their concern for others in distress. For example, a study published in 2011 conducted by Inbal Ben-Ami, Jean Decety, and Peggy Mason working at the University of Chicago provided the first evidence of empathy-driven behavior in rodents (please see "Empathic Rats Free Known Trapped Rats From Being Restrained"). Appearing in the prestigious journal Science, the results of this landmark study showed that untrained laboratory rats will free restrained companions and this helping is triggered by empathy (Ben-Ami Bartal, I., Decety, J., & Mason, P. 2011. Empathy and pro-social behavior in rats. Science, 334, 1427-1430). They'll even free other rats rather than selfishly feast on chocolate. We also know that social experience and familiarity play a role in this prosocial behavior.
Building on what is known about laboratory rats, James Burkett and his colleagues at Yerkes National Primate research Center have shown that prairie voles, a highly social rodent, show an empathy-based consoling response toward distressed friends, but not toward distressed strangers. In a paper published in Science (not available online) called "Oxytocin-dependent consolation behavior in rodents," the researchers write in the abstract:
"Consolation behavior toward distressed others is common in humans and great apes, yet our ability to explore the biological mechanisms underlying this behavior is limited by its apparent absence in laboratory animals. Here, we provide empirical evidence that a rodent species, the highly social and monogamous prairie vole (Microtus ochrogaster), greatly increases partner-directed grooming toward familiar conspecifics (but not strangers) that have experienced an unobserved stressor, providing social buffering. Prairie voles also match the fear response, anxiety-related behaviors, and corticosterone increase of the stressed cagemate, suggesting an empathy mechanism. Exposure to the stressed cagemate increases activity in the anterior cingulate cortex, and oxytocin receptor antagonist infused into this region abolishes the partner-directed response, showing conserved neural mechanisms between prairie vole and human."
This landmark study has understandably received a good deal of attention in popular media, and an apt summary reads as follows:
"A new study reveals that prairie voles console loved ones who are feeling stressed -- and it appears that the infamous 'love hormone,' oxytocin, is the underlying mechanism. ...The researchers created an experiment where relatives and known individuals were temporarily isolated from each other, while one was exposed to mild shocks. Upon reunion, the non-stressed prairie voles proceeded to lick the stressed voles sooner and for longer durations, compared to a control scenario where individuals were separated but neither was exposed to a stressor. Measurements of hormone levels revealed that the family members and friends were distressed when they could not comfort their loved one."
It's interesting that prairie voles, but not meadow voles, show this oxytocin-based consoling behavior, and in the original essay published in Science, the researchers also note (numbers refer to references in this report),
"The presence of consolation behavior in prairie voles demonstrates that this behavior does not require advanced cognitive capacities, and the conserved neurobiology of consolation between prairie voles and humans suggests a deep homology of the underlying neural substrates. The ancestral biological mechanisms supporting maternal care in mammals have likely served as the basis from which many complex social behaviors evolved, including empathy (24, 36) and pair bonding (37), both of which involve the reorienting of parental behaviors toward adult conspecifics. Nonetheless, the confirmed absence of consolation in the closely related meadow vole and in most macaques (9, 38) shows that consolation behavior emerges only under particular social and evolutionary conditions."
A few people asked me how this latest study on prairie voles differed from the work on rats, and Dr. Frans de Waal, one of the co-authors on this latest study, told me that the studies on rats, "did not show consolation behavior (trying to reduce another's distress thru body contact), but did strongly suggest that empathy underlies the rat's altruism response, so yes a related finding."
Please stay tuned for more on the fascinating emotional lives of rodents and other animals. There is still so much to learn about just whom other animals are and how they care for others in need.
Marc Bekoff's latest books are Jasper's Story: Saving Moon Bears (with Jill Robinson), Ignoring Nature No More: The Case for Compassionate Conservation, Why Dogs Hump and Bees Get Depressed: The Fascinating Science of Animal Intelligence, Emotions, Friendship, and Conservation, Rewilding Our Hearts: Building Pathways of Compassion and Coexistence, and The Jane Effect: Celebrating Jane Goodall (edited with Dale Peterson). (Homepage: marcbekoff.com; @MarcBekoff)