The Expression of the Emotions in Man and Animals Chapter IV - Means of Expression in Animals Part 2

In which various animals, from birds to reptiles and mammals, display the erection of hairs, feathers, or scales as an involuntary reflex often triggered by anger or fear, serving to increase their apparent size and intimidation. This natural phenomenon is accompanied by deliberate movements and vocalisations, signifying a complex interplay between instinct and habit shaped through generations for purposes of defence and combat.