Unlike other wild horses, Gunner isn't afraid of Erica's headcollar or the fact it links her to humans, since he's lived with the Lakota for a part of his life. As such, he doesn't run from her or avoid her. Instead he feels sorry for this lonely, fearful mare, and takes her into his herd to look after her.
This scene felt right for these two. Plus, the stallion render gave me a chance to show Gunner's gorgeous heterochromia ^^
Gunner (c) Nimfea
Erica and renders (c) me
Background and original images (c) Dreamworks Spirit:SoTC