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Aggression: fear



  • Fear can be a normal, adaptive response, given the context. When the fearful behavior is out-of-context and normal behavioral responses are replaced by those characterized by intensive arousal and active avoidance or withdrawal, a diagnosis of fearful behavior may be involved.
  • Because of the nuances of the neuroendocrine arousal system in cats, the majority of cats who are fearful are also aggressive.
  • A description of behaviors that manifest when fear and aggression are both involved may relate to 2 diagnoses:
  • Clients complain about fear aggression primarily when humans are the foci of the attacks; however, fear aggression can focus on other cats or animals of any other species.



  • These abnormal cats may have a genetic predisposition, or may have had incomplete exposure to other cats while growing up.  There is insufficient data on all of these topics, so no firm conclusions can be drawn; however, cats whose parents - particularly the fathers - are friendly and who were not socially deprived as youngsters have the best chance of avoiding being afflicted with these conditions.
  • A full understanding of the inheritance of temperament is lacking but it is likely that the presence on the X chromosome of genes for many neurotransmitters plays a role.

Predisposing factors


  • Primary fear aggression may be a sequelae to abuse or a condition that develops naturally because of aberrant neurotransmitter function.  Additionally, secondary fear aggression may be a sequelae to aggression due to lack of socialization.  We should also consider the dynamics of abandonment.  If cats who are 'genetically' fearful are abandoned more frequently, the group of cats for whom aggression due to lack of socialization may be a first step in the etiology of fear aggression would not be a heterogeneous one.  This is important for prognosis.  A cat that is 'genetically' fearful may not be as able to respond to early social exposure as a cat without that burden, but together, factors suggest that even with huge amounts of intervention improvement may be limited.


  • For cats whose primary concern is aggression due to lack of socialization Lack of appropriate socialization and/or habituation, there is invariably a history of early lack of exposure to or interaction with humans, cats, or another species.
  • Cats who have not had contact with humans prior to 3 months of age have missed sensitive periods important for the development of normal approach responses to people.
  • Lack of such socialization with other cats may result in the same lack of normal inquisitive response to other cats.
  • Furthermore, total isolation from cats can have negative consequences for future interaction with humans.
  • This constellation of deprivation scenarios may be contributory to many of the aggressions seen in urban, feral cats, in which case the development of fear aggression may be secondary.
  • For cats whose main concern is primary fear aggression it is important to remember that there are genetically friendly cats and genetically shy cats.  The extent to which a cat has the potential to be outgoing depends on paternal genes.   It is unclear the extent to which shy cats have the potential to become fearfully aggressive, but there are cats who, despite the best early exposure possible, become aggressive whenever fearful.  These cats also may become fearful without an apparent stimulus.  Once reactive at all, the threshold for aggression and further reactivity in these cats is considerably lowered.
  • Cats may also become fearfully aggressive as an adaptive learning response to abandonment, inappropriate housing in shelters, and abuse.  Regardless, if truly threatened, any cat - even a "normal" cat - will defend itself.  The only issue is where the threshold for reactivity lies.  Depending on the outcome of the treat, the cat that responds appropriately, in-context can also learn to become fearfully aggressive.
  • Concomitant or co-morbid diagnoses are the rule in behavioral conditions owing to the numerous associations created under conditions of anxiety and stress.
  • Behavioral,  renal/urologic, and dermatological conditions are commonly seen together.  Unfortunately, when a physical or somatic sign is apparent the tendency is to ignore the behavioral signs, to not ask about them, or to assume that these will resolve when the medical condition is addressed.
  • More often than not the reverse may be true: once the behavioral situation is addressed, many physical conditions improve or resolve, and without changes in the behavioral environment, many physical situations become chronic.
  • Any organ system that can be affected by stress may be affected in the complex situation that is represented by fear aggression.  Also, because these cats are extremely difficult to handle they may not have their conditions diagnosed until they are advanced.
  • Because veterinary visits often contribute to making these patients worse clients may avoid or delay a veterinary consultation.


  • Like almost all other behavioral conditions (except for extreme types of fear like panic and phobias) the longer that the aggression has been ongoing the better honed the skills of the aggressor.  Social maturity is a risky period because of the changes in neurochemistry and the tendency of all social species to explore more and emerge from or leave their natal groupings.  If clients can learn to recognize normal fear responses and truly judge when their cat - regardless  of age - deviates from contextually appropriate responses, they will be able to seek help early for cats that have both primary and secondary fear aggression.  The earlier that intervention begins, the more likely that they are able to favorably alter the time course of the condition.  Clients and veterinarians need to remind themselves that no matter how minor the upset seems to them, every single time a troubled animal exhibits a fearfully aggressive response they are practicing the response and coding that response into their molecular neurochemistry.  Learning augments both desirable and undesirable behaviors.


  • Social learning involves a gradual and ongoing process that also takes into account ontogeny and maturity. Whether social learning is less likely to occur normally for either the genetically fearful cat or for the one deprived of social exposure is an unexplored question.  That said, if genetics places subgroups of cats at more risk for abandonment, early intervention might not be possible because these cats may have also missed exposure during the relative sensitive periods.  These are important concerns for welfare organizations and rescue groups.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Overall K L (2004) Paradigms for pharmacologic use as a treatment component in feline behavioral medicine. J Feline Med Surg 6 (1), 29-42 PubMed.
  • Levy J K, Woods J E, Turick S L & Etheridge D L (2003) Number of unowned free-roaming cats in a college community in the southern United States and characteristics of community residents who feed themJAVMA 223 (2), 202-205 PubMed.
  • Lowe S E & Bradshaw J W S (2001) Ontogeny of individuality in the domestic cat in the home environment. Anim Behav 61 (1), 231-237 PubMed.
  • Munro H M & Thrusfield M V (2001) Battered pets: sexual abuseJ Sm Anim Pract 42 (7), 333-337 PubMed.
  • Munro H M C & Thrusfield M V (2001) Battered pets: features that raise suspicion of non-accidental injury. J Sm Anim Pract 42 (5), 218-226 PubMed.
  • Munro H M C & Thrusfield M V (2001) Battered pets: injuries found in dogs and cats. J Sm Anim Pract 42 (6), 279-290 PubMed.
  • Kessler M R & Turner D C (1999) Effects of density and cage size on stress in domestic cats (Felis silvestris catus) housed in animal shelters and boarding catteries. Anim Welf  8 (3), 259-67 VetMedResource.
  • Overall K L (1998) How understanding normal cat behavior can help prevent behavior problemsVet Med 93 (2), 160-171 VetMedResource.
  • Overall K L (1998) Managing an aggressive catVet Med 93 (12), 1051-1052 VetMedResource.
  • Seksel K & Lindeman M J (1998) Use of clomipramine in the treatment of anxiety-related and obsessive-compulsive disorders in catsAust Vet J 76 (5), 317-321 PubMed.

Other sources of information

  • Overall K L (2004) Manual of clinical behavioral medicine for small animals. Elsevier, St. Louis.
  • Horwitz D, Heath S, Mills D (2002) BSAVA Manual of canine and feline behavioural medicine. BSAVA, Gloucester UK, 2002.
  • Casey R A (2001) Pathological consequences of environmentally induced stress in domestic cats. Proc 3rd Internat Cong Vet Behavioral Med (Overall KL et al, eds), UFAW, Potters Bar, UK, pp 30-36.
  • Seksel K (2001) Training your cat. Hyland House, Australia.
  • Beaver B V (2000) Feline behavior: a guide for veterinarians, 2nd edition, WB Saunders, Philadelphia.
  • Ascione F R, Arkow P (1999) Child Abuse, Domestic Violence, and Animal Abuse. Purdue University Press, West Lafayette, IN, 1999.
  • Coffey J, Seksel K (1998) Kitten Kindy: an information guide (unpaged) and accompanying video ASAVA and Uncle Ben's of Australia, 1998.
  • Olson P, editor (1998) Recognizing and Reporting Animal Abuse:  A Veterinarian's Guide, American Humane Association, Englewood, CO, 1998.
  • Overall K L (1997) Clinical behavioral medicine for small animals. Mosby, St. Louis.

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