This paper describes the tail movements of ungulates, canids and felids, and the situations which elicit them. In this way the cause and function of tail movements for communication are considered. Tail movements can be divided into dorso-ventral (that is elevation and depression) which are closely associated with changes in postural tonus, and lateral tail movements (tail wagging). These tail movements are reported in detail in pigs, cattle, horses, goats, dogs and cats, together with the contexts that give rise to them. Information from personal observations and the literature in a number of other species is also reported. It is found that tail elevation and a high postural tonus are correlated and indicate a preparation for locomotion, and an increase in pace. In this way upright postures have become of communicative value to indicate a preparation for locomotion, alertness and thus warning. They are also used in confident approach and ofen associated with aggressive intentions. In some species this posture has become exaggerated specifically, to increase its signal value. A drop in postural tonus is shown to be related to fear. Postures of low tonus, combined often with a protective withdrawal of the tail and ears, are characteristic of fearful situations and have therefore become of signal value indicating fear and in social contexts, non-aggression and submission. Exaggeration of these postures is evident in some species. Lateral tail movements originated in association with locomotion (e.g., in fish). It is shown that there is still an association of lateral tail movements with locomotion in the mammals considered, although this is often particularly evident where locomotion is frustrated or inhibited. Cutaneous stimulation has become particularly important in eliciting lateral tail movements in some species. It is shown both from observational and experimental data, that lateral tail movements tend to occur particularly in approach/avoidance conflict and frustrating situations. Lateral tail movements have much in common in cause with preening movements in birds, head shaking and ear flicking which have been shown to occur as transitional activites between bouts of ongoing behaviour. In some cases tail wagging, like preening in birds, has become exaggerated and its association with the above situations ensures that a message is transferred by it with information about the communicators general motivational state. However sometimes it is also associated with a more specific message (e.g., tail wagging as an intention to kick in the horse, or as an indicator of non-aggression and 'friendliness" in the dog). An increase in postural tonus and tail wagging occur in many different situations. What all of them have in common is that the animal is 'excited'. This is defined and it is suggested that 'excitement' could be a useful descriptive term. Thus a common causal model is proposed for the elevation, depression and lateral movements of the tail in ungulates, canids and felids. Although there has been an emphasis in some species on particular types of tail movements in specific situations for use as visual signals, nevertheless most movements of the tail in these widely differing species can be shown to be associated with locomotion, only lateral movements are, in some species also associated wih cutaneous irritation. There is no evidence to suggest however that there has been an emancipation of causation, although some tail movements are exaggerated and otherwise ritualized.
