In the wild, animals may share waterholes, and grazing areas. Some animals have symbiotic relationships one example being the hippopotamus and the oxpecker bird. The symbiotic relationships are based on needs; Hunger, shelter, safety.
Human beings, appear to be the only species that has relationships with other species for pleasure. Companion animals and horses for riding are two examples. Of course, there is also the use of animals to meet the species needs; eg dogs for safety.
In this question I would like to focus on the relationship between human beings and other species as a source of pleasure (or comfort).
What is different within the human brain that allows humans to maintain relationships with other animals purely for pleasure, that is absent in other species?