Wistar rats raised in an affectionate environment display lifesaving-like behaviors while distinguishing life from death

Abstract

It is generally believed that humans are the only species that values life. However, it is not well understood whether animals have a nature that values life. In this study, we attempted to determine whether male Wistar rats have this nature. Normally-reared rats did not show lifesaving-like actions towards anesthesia-induced comatose rats, although they seemed to distinguish life from death. Considering the possibility that different rearing conditions may foster a life-valuing nature, male Wistar rat pups were reared in several ways: normal rearing, loving rearing (LR; rats reared as if they were cute pets), rearing in an enriched environment, reared with gentle stroking of the back, and normal rearing of offspring of rats raised under LR conditions. When placed in an anxiety-producing environment, only LR rats escaped into the hands of the person who reared them, indicating attachment. Only the LR rats displayed lifesaving-like actions towards unknown comatose rats or drowning pups. LR rats also stopped attacks by biting ICR mice that were attacking C57BL/6 mice. Thus, rearing in an affectionate environment may foster a life-valuing nature, even in rats, suggesting that the valuing of life may be neither innate nor human-specific.