I would be glad to give my thoughts on it, but let me ask some questions to get a feel for what these dream images might mean to you.

What do you associate with bison in general, with the adults or the babies? What qualities do they have?

Animals can represent all sorts of things about people, including a more basic level of being (the level on which we breathe and our heart beats and we walk through nature). Can you draw a connection between a bison and any qualities within yourself? A bison could represent a higher level of being for you, such as a fully integrated state of being in which all parts of you are drawn into unity or you are drawn into a spiritual experience.

The dream seems to be suggesting that the mama Bison is no longer going to be able to care for her calf, and you are given that job. You are given the job of protecting and nurturing the calf. It is like you take over for her. Does that seem to resonate?