and Mother Wolf’s neck-bristles lifted as the time came – Father Wolf pushed “Mowgli, the Frog,” as they called him, into the center, where he sat laughing and playing with some pebbles that glistened in the moonlight.
The imagery in the passage shows Mother Wolf's "neck-bristles lifted." This shows that she is anxious or nervous about presenting Mowgli to the Pack. She most likely wants to protect him and will defend him if he is threatened.
