Answer:
She realized the wolves would soon depart for their nomadic winter life.
Step-by-step explanation:
The open tunnel was used as a shelter for the young as they grew up and became strong enough to walk and run. This moment indicated that the wolves would begin their migrations and live like nomads during the winter. It was this thought that scared Miyax, as she saw that the cubs had already reached the strength necessary for the migration, which meant that the wolves would soon be gone.