Joaquin Phoenix and John C. Reilly play assassin brothers Charlie and Eli with the unlikely last name of “Sisters” in “The Sisters Brothers.” The film shot in Spain and the two actors spent a lot of time together off-set as well, bonding with each other. And their horses.

Reilly told GQ his horse was named Pollito—Little Chicken. Reilly stopped by the stables on weekends to feed Pollito apples.

His affection for Pollito extended to a profound appreciation for all horses:

“There’s this beautiful thing that happened where, somewhere in ancient history, a horse decided, I’m going to allow you to ride me. I’m going to allow you to tie me to this wagon so you can move these things.” Without that decision, and without that cooperation from that animal, we would have nothing that you can see here. Nothing. We would be fucking running around with bones and furs on our back. Really! Think about it! That relationship is the foundation of civilization. There’s no other animal that’s that cooperative and that’s strong enough to do the things we need horses to do.”

He told Business Insider, “I developed a deep, deep bond with my horse. At the end of the movie, I thought, it’s going to be so emotional to say goodbye to the people, but the only time I cried was when I said goodbye to the horse.”

As he said to GQ, he’s a horse lover for life. “Damn, I’m telling you, man. I don’t know if you’ve ever spent much time with horses. But they’re miraculous creatures!”

[SPOILERS for the film: Does the horse live?]