Since dogs cannot talk, their body languages are used to interpret whatever emotion or feeling they may be experiencing.
When a dog is afraid, she tries to look small. She lowers her body and and leans away so that her center of gravity is over her hind legs to make a quick retreat easy. She also puts her tail down and ears flattened back to her skull. Her eyes also look rounder than normal and she shows the whites of her eyes (whale eyes).
All these tell that a dog is scared and worried or feeling tense.
