Their conversation happens with their eyes. No words. But thereafter it was established that he offers the fox food (e.g., bread or leftover something) & the fox will leave his chickens alone.
Once he forgets his side of the bargain. So the fox strikes. The author realizes and resumes performance of his side of bargain.
The author, I recall, comes from a very severe case of domestic violence (by his father). He talks about it in the book too.
/2