Why is My Dog/Cat Aggressive?

In dogs and cats, aggression refers to aggressive behavior towards conspecifics or towards humans, stemming from various causes. In some cases, especially in dogs, aggressive behavior is also directed against objects.

As a rule, aggressive behavior in dogs and cats is not a disease; rather, the behavior lies within the normal behavioral spectrum of the animal species. These forms of Aggressiveness usually develop gradually, are sometimes linked to sexual maturity, and/or develop through learning. They can be influenced by training.

In rare cases, organic causes can also be responsible for aggressive behavior. These forms of Aggressiveness can only be influenced by eliminating the causes.

Aggressiveness within the Normal Behavioral Spectrum of the Animal Species

• Dominant behavior (hierarchy position)
• Defense of a sexual partner
• Defense of one’s own territory
• Defense of one’s own pack
• Defense of specific objects
• Aggressiveness due to Uncertainty / disorientation
• Aggressiveness as a result of Pain
• Aggressiveness as a result of stress (cats)

Aggressive Behavior with Organic Causes

• Hormonal, metabolic, and biochemical changes:
  Administration of medications and hormones (testosterone, cortisol, thyroid hormone)
  Altered ratios of hormones to each other (spaying of the female dog, hypothyroidism)
  Disturbed ratios of neural messengers in the brain (serotonin/dopamine metabolism)
• Infectious diseases, organ diseases
  Rabies
  Distemper
  Toxoplasmosis
  Lyme disease
• Organ diseases
  Hydrocephalus
  Epilepsy
  Portosystemic shunt
  Circulatory disorders in the brain
  Tumors in the brain
• Brain injuries
• Poisoning (lead, organophosphates)

Treatment

Unwanted behavior and/or learned behavior can be well influenced by appropriate training and only rarely requires the support of a veterinarian. In case of serious problems, the help of a competent animal trainer is useful.

If the Aggressiveness is due to Pain, it is of course urgently necessary to determine the cause of the Pain and treat it accordingly with veterinary medicine.
In cats, a lot of patience and species-appropriate handling are necessary to enable a relaxed interaction with them.

If, on the other hand, aggressive behavior can be attributed to hormonal, metabolic, and biochemical changes as well as various infectious and organ diseases, a successful treatment of these will also lead to the disappearance of the aggressive behavior.