The 'old granny fox story' could potentially be a moral tale. Perhaps it shows how the old granny fox, despite being old, still has valuable lessons to teach. It could be that she teaches the younger foxes about the importance of being patient when hunting, or how to be kind to other animals in the forest even if they are potential prey. In some versions, she might even have a magical element to her, like being able to communicate with the spirits of the forest to gain knowledge and help for her family.
I'm not sure which specific 'old granny fox story' you mean. There could be many folktales about an old granny fox. Maybe it's a story about a cunning old fox who outsmarts other animals in the forest.
Well, the 'old granny fox story' might be one where the old granny fox has some sort of adventure. For example, she could be on a quest to find a special food for her family during a harsh winter. She might use her wisdom and experience, which she has gained over the years, to overcome various obstacles like tricking other animals into revealing where the best food sources are.