Behavior Aberrant

John J. McGlone Nadege Krebs

Texas Tech University, Lubbock, Texas, U.S.A.


Aberrant refers to something that deviates from the usual or natural type. Interchanged in the literature with the term aberrant is the term abnormal in reference to deviations from normal behaviors. Abnormal behavior has been defined as behavior ''that deviates in form, frequency, or sequence from a defined, comparable standard. Such a standard may be a behavioral inventory typical for a given genotype, age group, sex, nutritional level, housing condition, or management system, etc.''[2] Behaviors are not classified as aberrant or abnormal simply because of their level of behavioral frequency or duration. Some behaviors are expressed at a low frequency, yet they are critical (example: defecation is an infrequent, yet critical behavior). In contrast, tongue rolling in calves may be expressed at a low frequency, but it lacks purpose and thus can be classified as an aberrant behavior. To be classified as aberrant, a behavior must be lacking purpose; harmful to the animal, other animals, or property; or maladaptive. To suggest a behavior lacks purpose requires a complete understanding of the context of the behavior and the evolutionary development of the species. For example, some ritualized sexual displays may at first seem to lack purpose, but they have been incorporated into sequences of behaviors that on the whole are adaptive.

TYPES OF ABERRANT BEHAVIORS Self-Directed Aberrant Behaviors

These are directed at the animal or at inanimate objects. These may or may not injure the animal.[1,2]

Stereotyped behaviors are behaviors that vary little in form, sequence, and time. Chewing food is a stereotyped behavior. Rumination is a variation of chewing that is found in a highly stereotyped form in cattle. Some behaviors occur regularly, but are a special form of stereotyped behavior referred to as stereotypies. Stereotypies are stereotyped behaviors composed of relatively invariant sequences of movements that serve no obvious purpose.

Many examples of self-directed aberrant behaviors are given in Table 1. Some behaviors are directed toward the animal itself (including to the air)[4,5] and some are directed toward components of the environment. Some self-directed aberrant behaviors can be harmful to the animal. Others seem obsessive-compulsive in nature.

Some stereotypies are thought to be related to feeding motivation[6] in that restricted feeding may increase the rate of expression of stereotypies. In sows, stereotypies can be present 10 15% of the time; in horses, the average can be 8%, but can reach 30% in racing stables.[7] Ruminants express less stereotyped behaviors,[8] but they may show tongue rolling or other forms of oral behaviors. Brain mechanisms that cause stereotypies are not known, but they may be related to the brain dopamine system involved in the control of movements and to opiate peptides.[9]

Social Aberrant Behaviors

These are directed toward other animals of the same species or toward other species.

Aberrant behaviors directed toward others can be damaging to the body of animals receiving the behav-ior.[10] Tail biting,[11] feather pecking, and wool-pulling are relatively common aberrant behaviors. Other aberrant social behaviors that do not involve oral behaviors include excessive mounting as in the Buller Steer Syndrome.[12] The Buller Steer Syndrome is not considered a reproductive behavior because it is usually observed among castrated males. Injury from oral and nonoral aberrant behaviors can be severe because modern confinement systems have limited space that does not allow flight from the offending animal(s).

Parental-Neonatal Aberrant Behaviors

These include those shown by the mother or father toward the young, or of the young toward their mother.[13,14]

The mother may not accept her newborn. This problem can have life-threatening consequences to the neonatal animal. Lack of acceptance of the neonate is found in all farm mammal species. Besides ambivalence of the mother toward her newborn, some mothers (and fathers) actually attack and, if allowed, will kill their offspring.

Table 1 Examples of aberrant behaviors and possible causes among farm animals

Type of behavior

Description of the behavior

Possible causes

Overeating, anorexia, polydipsia

Abnormal standing and lying or abnormal postures; changes in activity (hyper or hypo active); hysteria; pacing; weaving

Self mutilation; mutilation of others

Oral nasal facial (ONF) behaviors such as sham chewing, tongue rolling, bar biting, licking, cribbing, drinker pressing, anal massage, belly nosing, intersucking, wind sucking, eye rolling Aggressive/agonistic behaviors

Neonatal rejection; maternal failure; stealing young; killing young/cannibalism

Reproductive behaviors; mounting; silent heat, impotence; coital disorientation; intromission impotence, inappropriate mounting

Excess or reduced eating or drinking

Aberrant frequency, duration, or sequence of standing, lying, posture or locomotion; ataxia; head shaking or nodding

Vigorous body mutilation; excessive rubbing, licking, biting, chewing; kicking directed at self or other animals; feather or body pecking; wool pulling; tail biting; egg eating; Buller Steer Syndrome (excessive mounting to the point of injury) Movements of the mouth without food present. Generally associated with standing, sitting, or lying, mouth and face movements; may have frothing and foaming Excessive threat or attack of another animal (or of human); movements of head (bite), butting and kicking (cattle, horses), biting (horses), chasing (poultry), charging (goats and sheep) First day postpartum desertion or aggression (butting, striking, driving away, biting); more common in first parity; unresponsiveness of the mother

Mounting, Excessive dysfunctional sexual technique

Abnormal brain chemistry, (ex. of hypothalamus?) Slippery floors Lack of space (therefore, weakness) and movement, weak legs because lack of calcium (osteomyelitis, osteoporosis), infectious disease Parasitism, gastrointestinal problems, pain, confinement and isolation; early weaning

Individual housing, lack of oral stimulation or enrichment

Confinement, housing system effects; inappropriate olfactory environment; restricted space

Separation from newborn, breed, disturbance at parturition, genetic, stress, crowding, Rearing system (isolation), possibly low estrogens or progesterone Isolation in monosexual groups High densities, hormone administration, vaccine, stress, genetics, inexperience, confinement

The precise physiological mechanisms of aberrant behaviors are not known. (Adapted from Ref. [3].)

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