This video from the USA says about itself:
Study On Prairie Voles Sheds Light On Animal Empathy
22 January 2016
Now, scientists have added the prairie vole to the list which already includes more mentally advanced animals like dogs and elephants. In the experiment, pairs of voles who knew each other were separated, and one received mild shocks. When they were reunited, the non-stressed members licked their partners longer and sooner than in other trials where neither had been stimulated. Distress hormones also increased in those who could not provide enough comfort. Adding to the evidence of empathy is that these responses were not observed among pairs of strangers. Oxytocin, which is known as a love hormone, has been attributed as a possible factor in this behavior.
Dynamic corticostriatal activity biases social bonding in monogamous female prairie voles
31 May 2017
Adult pair bonding involves dramatic changes in the perception and valuation of another individual. One key change is that partners come to reliably activate the brain’s reward system, although the precise neural mechanisms by which partners become rewarding during sociosexual interactions leading to a bond remain unclear.
Here we show, using a prairie vole (Microtus ochrogaster) model of social bonding, how a functional circuit from the medial prefrontal cortex to nucleus accumbens is dynamically modulated to enhance females’ affiliative behaviour towards a partner. Individual variation in the strength of this functional connectivity, particularly after the first mating encounter, predicts how quickly animals begin affiliative huddling with their partner. Rhythmically activating this circuit in a social context without mating biases later preference towards a partner, indicating that this circuit’s activity is not just correlated with how quickly animals become affiliative but causally accelerates it.
These results provide the first dynamic view of corticostriatal activity during bond formation, revealing how social interactions can recruit brain reward systems to drive changes in affiliative behaviour.