I can imagine a time when Balto and Steele were younger and perhaps could have once been friends and as some best friends slowly fall apart cracks can appear in the relationship and things can grow cold and hostile.
Note that Steele is not wearing his normal collar and I am blaming this drift in the friendship due to Steele's rise in popularity when he earned his collar and became lead dog.
The main outline of this image is how time can change people and how very few friendships can last the stress of time and change.