The links above and below lead to the web sites where you can find more on the subject of animal friendships. Also, the British newspaper The Sun has a whole gallery of pictures of interspecies friendships.
At right: Peter and Sammy, submitted by Jenn DeTullio of Freehold, NJ to the ASPCA web site.
Some years ago, on the subjects of interspecies relationships and what constitutes a "wild" animal, John Williamson of Tiger Touch had this to say:
It is not all that uncommon for lions, (and other species) male and female, to adopt other animals as "pets" or companions with which they interact to the benefit of both. Social bonding for purposes other than "natural" can be seen across a wide range of species. Witness humans and their mutually content companions. You might want to add socialization to your list of "innate" behaviors, the expression of which can take on a wide variety of forms depending on individual animals and their environmental constraints. "Wild" behavior only reflects a narrow range of expressions under certain conditions. There is very little "innate" about it. Being alive is innate, the possibilities thereafter take on an awesome, wonderful complexity within life's web...