How do we bond to one another? While in some species, like humans, physical contact plays a role in the process of attachment, it has been suggested that tactile contact's value may greatly differ according to the species considered. Nevertheless, grooming is often considered as a pleasurable experience for domestic animals, even though scientific data is lacking. On another hand, food seems to be involved in the creation of most relationships in a variety of species.
Sankey, C., Henry, S., Górecka-Bruzda, A., Richard-Yris, M. A., & Hausberger, M. (2010). The way to a man’s heart is through his stomach: What about horses? PLoS ONE, 5(11). https://doi.org/10.1371/journal.pone.0015446